The Science Notebook
Gilbert Chemistry - Part 9

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NOTE:  This book was published in 1936 as a manual to accompany several Gilbert Chemistry sets of the time.  While some of the experiments and activities here may be safely done as written, a number of them use chemicals and methods no longer considered safe.  In addition, much of the information contained in this book about chemistry and other subjects is outdated and inaccurate.  Therefore, this book is probably best appreciated for its historical value rather than as a source for current information and good experiments.  If you try anything here, please understand that you do so at your own risk.  See our Terms of Use.
Pages 161 - 180
GILBERT CHEMISTRY 161
 
each day taste a little of the cider.  You will notice that it becomes more sour daily, and that finally it will have become unfit for drinking and has turned into vinegar.  This is a well-known case of fermentation brought about by means of a bacterial organism.  The sweetness of the original cider is due to the presence of sugar.  By the prolonged action of a special low form of organic life the sugar is transformed into acetic acid.  Test your original cider and the final fermented product with a blue litmus paper.
 
EXPERIMENT 528 - Souring of milk
Take a tumbler of sweet milk and set it in a warm place where you can watch it.  Observe the changes that take place day by day.  The milk will become infected with bacteria and undergo fermentation with formation of lactic acid.  This organic acid is formed from the milk sugar in the fresh milk.  The lactic acid causes the milk to curdle.
 
EXPERIMENT 529 - Artificial butter
Oleomargarine is an artificial butter made from cotton seed oil and other vegetable oils.  It is a wholesome food product and is not necessarily inferior to real butter made from cow's milk.  Renovated butter is a process butter made from rancid butter by a chemical process.
 
EXPERIMENT 530 - Testing butter
Place a small lump of pure butter in a silver spoon and heat over your alcohol lamp.  Good fresh butter will melt and boil over, producing at the same time some foam.  If it is an oleomargarine preparation it will sputter and crackle. giving a sound like that of a burning green stick.
 
EXPERIMENT 531 - Testing butter
Heat a small pan of sweet milk to boiling.  When hot add a teaspoonful of butter to be tested and stir until melted.  Now pour into a tumbler and cool while stirring.  The added butter will solidify when the milk is cooled to ice temperature.
 
EXPERIMENT 532 - Testing butter
Repeat the preceding experiment using a sample of artificial butter.  When the milk is cooled the renovated sample will solidify in a granular condition and be distributed through the milk in small particles.  Oleomargarine will solidify to one cake and may be lifted from the milk with a spoon or stirring rod.
 
EXPERIMENT 533 - Milk and the common cold
Fresh pure milk is a perfect food and contains necessary vitamins for promoting growth.  Faithful use of this food will aid in protection against the common cold.  The true cause of a cold is not known but it is known that a diet high in vitamin A shortens a cold's duration and lessens its severity.  Therefore, eat foods rich in this vitamin.  Some of these are the following: milk, butter fat, cream, cheese, eggs, liver, cod-liver oil, fish   liver oils, red salmon, green and yellow vegetables, fruits, tomatoes and olives.
 
EXPERIMENT 534 - Changing cider into vinegar
Put two or three drops of vinegar in a glass full of cider and stir a few times with a stirring rod. Taste a little of this mixture and notice that it still has the characteristic cider taste.  Now set it aside in a moderately warm place for a few days and again taste a little of the cider.  After several days you will notice that the cider has a very decided vinegar taste, having fermented into vinegar.
 
The small amount of vinegar which you added furnished the necessary organisms or ferments which started the fermentation of the cider into vinegar.
162 GILBERT CHEMISTRY

EXPERIMENT 535-The souring of milk
Set a half glass of milk aside in a warm place for several days and notice that the milk soon curdles or precipitates out and a mould forms on the surface of the milk.  This is another illustration of fermentation taking place with the formation of mould.
 
ESSENTIAL OILS AND PERFUMES
 
The use of perfumes dates back as early at 2000 years ago. For instance, in ancient India the sacred fires in the temples were perfumed with kusa or kus, the fragrant root of a native grass.  This odor is a constituent of many of the present popular perfumes as in the azurea bouquet perfumes.  In the early days of China and Egypt perfumes were used in the form of incense and even today the Chinese still burn large quantities of this material as a perfume.  All the ancient perfumery materials consisted of crude drugs, flowers, herbs, aromatic gums, resins and woods of the Orient, also many of the fragrant flowers which are used in making some perfumes today.  Perfumes are extracted from the crude materials, such as flowers, herbs, etc., in three different ways. First, by treating the finely ground material with oil or fats in which the perfume is soluble.  Second, by steam distilling the crude materials during which process the perfume passes over with the steam.  Third, by extracting or treating the finely ground materials with volatile solvents such as petroleum ether, carbon tetrachloride or chloroform.  The last process or treating the crude materials with a volatile solvent is the one most commonly used now.
 
For many years chemists throughout the world have been devoting much research to the synthesis or building up of these natural occurring perfumes until today a new industry has been made possible, the industry of synthetic perfumes and flavoring materials.  These materials can be made commercially at a much lower cost than when they are extracted from the natural occurring substances.  Besides this a great many chemical substances have been found which have most delightful odors and flavors, and which at the present time do not exist in nature as such. The synthetic materials of today are successfully utilized in goods of the highest grade and many odor and flavor effects would be impossible without them. 
 
Let us try making some sweet smelling oils and perfumes from flowers, fruits and spices.
 
EXPERIMENT 536 - Making rose water
Fill an iron or tin vessel half full of rose petals and add enough water to cover the petals. Now place the vessel on the stove and, when the water starts to boil, cover the vessel with a piece of absorbent cloth.  When the cloth is wet with water from the condensed steam, remove it and squeeze out the water into a cup.  Repeat this operation five or six times and then discontinue the boiling.  Smell the water in the cup and notice that it has the sweet odor of the rose.  
 
The rose oil which was originally in the petals volatilized, that is, passed off with the steam and condensed in the cloth along with the water.  This is the way oil of rose was made in the very early times. Today rose water is obtained by steam distillation in a little different manner.
 
EXPERIMENT 537 - Making geranium water
Prepare geranium water the same way as you prepared rose water in the preceding experiment, using the leaves and flowers of the geranium plant in place of the rose petals.  Notice this time that you have a liquid which has the characteristic geranium odor.
GILBERT CHEMISTRY 163
 
EXPERIMENT 538 - Making lilac water
Repeat Experiment 537, using lilac flowers in place of rose petals.  Notice this time that the liquid obtained has the characteristic lilac odor.
 
EXPERIMENT 539 - Melting violet water
You can make violet water the same way as you made rose water in Experiment 536 by using violet petals in place of the rose petals. Notice that the liquid obtained has the characteristic violet odor.
 
EXPERIMENT 540 - How to make sachet powder
Mix together in a mortar one teaspoonful of cloves, one teaspoonful of cinnamon, one teaspoonful of allspice and half a teaspoonful of vanilla extract.  Now obtain a cupful of dry geranium or sage leaves and grind them up into a powder by means of the pestle.
 
Mix the ground geranium or sage leaves with the mixture of cloves, cinnamon, allspice and vanilla extract and place the powder thus formed in a jar with a cover.  Notice the fragrant odor produced from this powder. You can vary the odor of this powder somewhat by using the dried petals of different flowers.
 
EXPERIMENT 541 - How to make incense
Place together in a mortar four measures of cinnamon, three measures of allspice and five measures of cloves. Grind this mixture by means of a pestle.
 
Now pour this mixture on a sheet of paper and mix it with eight measures of potassium nitrate.  Do not grind this mixture.  
 
Heat a little of this mixture in a spoon over a flame and notice the fragrant odor given off which resembles that of burning incense.
 
EXPERIMENT 542 - How to make wintergreen extract
Place some wintergreen berries in a mortar and grind them up by means of a pestle.  Pour the oil obtained into a test tube and notice the fragrant odor.  Taste a little of the oil and satisfy yourself that it is oil of wintergreen. 

EXPERIMENT 543 - How to make lemon extract
Remove the skin from a lemon by means of a sharp knife and grind it up in a mortar in the same way as you did in the preceding experiment. Pour the oil into a test tube and notice the fragrant odor. Taste a little of the oil.
 
EXPERIMENT 544 - How to make orange extract
Remove the skin from an orange, using a sharp knife, and grind it up the same as in Experiment 543.  Notice the fragrant odor.  Taste a little of this oil.
 
EXPERIMENT 545 - Potpourri sachet
Mix together in a mortar the following spices or any of them which you can obtain:  Half a teaspoonful of cloves, half a teaspoonful of allspice, half a teaspoonful of cinnamon and about half a teaspoonful of extract of vanilla.  Grind these materials together until they are thoroughly mixed.
 
Now obtain about a quart of dried rose petals and mix this spice which you have just prepared with the rose petals.  When it is thoroughly mixed you will find that it gives a very sweet, pleasant odor, and it can be used in sachets or put in jars, thus making rose jars.  Whenever the cover is removed from these jars the sweet odor will fill the room.
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EXPERIMENT 546 - Sage
One of our common plants which has a very sweet odor is the sage.  The leaves of this plant when dried retain their odor for a long time, and they can be used to good advantage in sachets and other places where a sweet smell is desired.
 
COLLECTED FROM THE MAILBAG
 
Experiments with Flowers
 
EXPERIMENT 547 - Action of ammonia on a violet 
Use a pint fruit jar with a tight cover and place in the bottom of the jar a mixture of ammonium chloride and calcium oxide to which several drops of water have just been added.  Ammonia will be generated.  Now attach the violet to a string or silk thread and suspend it in the fruit jar and replace the cover.  Note the change of color in the violet as it remains exposed to the ammonia gas.
 
EXPERIMENT 548 -
Repeat experiment 547 suspending different pansy blossoms in ammonia vapor.
 
EXPERIMENT 549 -
Ammonia gas and a red rose.
 
EXPERIMENT 550 -
Ammonia gas and a pink rose.
 
EXPERIMENT 551 -
Ammonia gas and a red tulip.
 
EXPERIMENT 552 -
Ammonia gas and petunias of different colors.
 
EXPERIMENT 553 -
Ammonia gas and red geraniums
 
EXPERIMENT 554 -
Ammonia gas and red carnations.
 
PRACTICAL CHEMISTRY
 
EXPERIMENT 555 - Heat by chemical reaction
Place six measures of crystalline sodium acetate which is obtainable at your store in the bottom of a test tube.  Heat the tube over your alcohol lamp and sodium acetate will melt in its water of crystallization to form a liquid.  Cool, after suspending a crystal of sodium acetate in the liquid.  Crystallization will set in with  evolution of heat.  Suspend a thermometer in the crystallizing fluid and note the rise in temperature.
 
EXPERIMENT 556-Freezing with chemicals
Place a glass upon a wooden block and pour water around the glass so that it stands in water. Fill the glass about three-quarters full of water and add one teaspoonful of ammonium sulphocyanide or ammonium nitrate and stir.  The glass will soon become frozen in the block.
GILBERT CHEMISTRY 165
 
EXPERIMENT 557 - Glycerine-litharge cement
Litharge (lead monoxide) which is obtainable in any drug store, is mixed with glycerine in various proportions depending on the use to be made of the cement.  If a slow setting cement is desired use pure glycerine.  If a quick setting cement is desired, dilute the glycerine equally with water.  This cement is useful for making water-tight connections between plumbing fixtures and porcelain.  It is very hard when it sets.
 
EXPERIMENT 558 - Casein-borax glue
Shake some pulverized borax with water until no more dissolves, using four ounces of water.  Now rub casein into a paste with the borax solution, adding the casein until a thick glue is formed.  Add a little copper sulphate solution as a preservative.  This is useful for repairing wood, porcelain and glass.
 
EXPERIMENT 559 - Protecting book bindings
a. Petroleum jelly is a fine preservative when rubbed into the covers.
b. Beeswax dissolved in gasoline is also excellent for treatment of book covers.

Lanolin can also be introduced with the beeswax to great advantage.
 
EXPERIMENT 560 - Stains for wood
Chemical solutions for staining wood are useful for many purposes in which a liquid color is wanted.

Chemical
Solution of potassium permanganate
Solution of copper chloride and pyrogallic acid
Potassium ferrocyanide and oxalic acid
Potassium ferrocyanide and ferrous sulphate
Ferric ammonium sulphate and tannic acid
Picric acid    		Color
brown
brown
blue
blue  
black
yellow

TEXTILE CHEMISTRY AND DYEING

Textile fibers may be grouped in two classes according to their source: vegetable fibers and animal fibers. Cotton, linen, and rayon are all of vegetable origin, the first two being the natural fibers as gotten from the cotton and flax plants, respectively, while rayon is a very interesting textile material produced by first dissolving the cotton substance, called cellulose, and then from the viscous liquid spinning a thin filament which is hardened chemically into a thread so fine and lustrous that it was originally called artificial silk.  But since its chemical and physical properties were in many ways unlike true silk, it was soon given a name of its own, rayon.  Cellulose is a common material in the woody structure of all plants and trees, so it is not  necessary to destroy good cotton fiber to make rayon.  It is of further interest that the solubilized cellulose enters the composition of many of of our lacquers, and also that, if formed into a sheet instead of line thread it becomes the well-known cellophane 
 
Silk and wool are produced by animals, the first being the cocoon of the silk worm, and the other, as you all know, is the warm coat of a sheep. These fibers are therefore very different from the cellulose group, and are spoken of chemically as proteins.  The chemical differences between these classes of textile fibers are important to remember, especially in connection with dyeing and with spot and stain removal.
 
The cellulose of vegetable fibers is very easily damaged by strong acids, but is uninjured by quite severe treatment with alkali.  These fibers do not combine with dyes
166 GILBERT CHEMISTRY
 
very readily, and it is frequently necessary to deposit the dye on the fiber in a water-soluble form, then convert it to an insoluble product, in order to hold it permanently on the fiber.
 
Animal fibers, on the contrary, are much more resistant to acid and more easily damaged by alkali than the vegetable fibers.  They combine with many dyes so firmly that the problem of dyeing colors fast to washing is greatly simplified.
 
Years ago most dyeing was done with the colored extracts of various plants.  There were a limited number of these and many of the bright colors so common today could not be obtained.
 
Gradually there were discovered ways of making new dyes in the laboratory, building them up from simpler compounds obtained, in many cases, from coal tar.  These dyes, sometimes called aniline dyes, now supply every hue of the rainbow and have almost completely displaced the natural dyes. 
 
TESTING TEXTILE FIBERS
 
EXPERIMENT 561 - The burning test
Obtain samples of several fabrics.  Take a few threads from a sample and light one end in the flame of your alcohol lamp.  If the sample is an animal fiber it will not burn rapidly but will char into little black knobs and will produce an odor like burning feathers or hair.  If the threads burn readily, leaving a clean white ash, they are vegetable fibers.  This test is particularly useful in recognizing whether a sample is silk or rayon. One type of rayon, cellulose acetate sold under the trade name  "Celanese,” does not burn readily like the other rayons, but more like silk, except that it does not give an odor like burning feathers.  Hence an additional test is needed if cellulose acetate is suspected of being present.
 
EXPERIMENT 562 - Acetone test for cellulose acetate
Moisten the textile fibers with acetone.  Ordinary animal and vegetable fibers are not changed, but cellulose acetate softens and may even dissolve completely. 
 
EXPERIMENT 563 - Microscopic examination 
With experience one can soon learn to recognize most of the fibers by appearance and feel.  A magnifying glass or microscope is a great help.  With it, wool is seen to have a rough scaly surface while silk is quite smooth. Rayon appears much like silk, but of course the burning test will show them different. The cotton fiber is seen to he an irregular, flattened tube.
 
EXPERIMENT 551 - Wetting test to identify linen 
Linen is more readily wet through than the other fibers.  This property is made use of in the following test.  Put a small piece of cloth in a test tube half full of water and add one measure of sodium bisulphate.  Heat the solution to boiling.  (Be sure that the sample is very small so that it does not prevent free circulation of water.)  Take out the sample, wash it several times with water and dry it.  After it is dry, loosen several of the fibers with a pin or needle and moisten them with a drop or two of glycerine.   Press the cloth between two blotting papers and then examine very carefully the fibers which were moistened with glycerine.  If they are linen they will be semi-transparent, while other fibers will appear opaque.
  
EXPERIMENT 565 - A quantitative test for fabric composition
The fact that caustic soda dissolves animal fibers without attacking vegetable fibers serves as a basic for one method of determining their percentage in a fabric.
GILBERT CHEMISTRY 167

Put six measures of calcium oxide and six measures of sodium carbonate in a glass containing two test tubes of water.  Boil for several minutes, then let stand to settle and pour the clear liquid, which is sodium hydroxide into a clean cup while you wash the solid residue from the glass. Return the sodium hydroxide solution to the clean glass.
 
Now take a sample of cloth which you suspect is made of a mixture of animal and vegetable fibers such as wool and cotton.  Weigh it carefully, then immerse it in the sodium hydroxide solution and boil it for a few minutes. This should dissolve any wool or silk.  Remove the remainder of the sample, rinse it in water, dry and weigh.  The  loss in weight represents the wool or silk which had been in the fabric.
 
DYEING
 
You will find it very instructive in the following dyeing experiment if you prepare small patches of cloth containing threads of several kinds. Cut squares of white cotton, about two inches each way. Cotton from an old sheet or pillow case is better than new cloth for by many washings the fibers have become easier to dye.  Next obtain coarse white threads or yarns of wool, silk, rayon, and linen.  With a needle, stitch one of each of these threads across each square of cotton, using long stitches to keep most of the thread showing on one side."  Trim the threads even with the edges of the patch.
 
EXPERIMENT 566 - Dyeing with an aniline dye
Aniline dyes are now supplied ready for household use, and the beginner will find these very interesting to experiment with.  You will undoubtedly find some on hand in the laundry.
 
Dye one of your patches of cloth in one of these dyes, following the directions on the package.  Are all the kinds of textile fiber in the patch dyed alike?
 
EXPERIMENT 567 - Using an aniline dye with a mordant
Dissolve five measures of tannic acid in one test tube of water in a glass.  Soak a patch of cloth in this solution for an hour or more.  Squeeze it out and dry it.  Now dye this patch with the same aniline dye and in the same way as in the experiment above.  When the dyed cloth has dried, compare it with the previous dyeing.  How has the tannic acid influenced the intensity of color on each fiber?
 
EXPERIMENT 568 - Dyeing with a natural vegetable dyestuff 
Dissolve three measures of ferric ammonium sulphate in one test tube of water and soak one of your cloth squares in this solution.  Remove the cloth, press it between layers of paper towel to remove excess liquid, and allow it to dry.
 
Next dissolve two measures of tannic acid in one test tube of water and soak the cloth in this solution. Press out the cloth and dry it again. 
 
Finally, put three measures of logwood into one test tube of water and boil it in your beaker until it is a bright red.  Put the cloth into this solution and continue to boil it a short time. Remove the cloth, wash it well in water, and dry it.  What color have you produced?  Are all the fibers dyed equally well?
 
EXPERIMENT 569 - Another black dying
Repeat the dyeing as above, but omit the logwood treatment.  Compare the quality of black in the two dyings.
 
EXPERIMENT 570 - Mordant dying with cochineal
Dissolve three measures of aluminum sulphate in one test tube of water in a beaker and soak one of your cloth squares in this solution.  Add two measures of sodium car-
168 GILBERT CHEMISTRY
 
bonate to the solution, stirring quickly and thoroughly. After a few minutes remove the cloth, squeeze out the water, and let it dry.
 
Next put one test tube of water in your beaker, add three measures of cochineal and boil until the liquor is a dark red. Now put the cloth in and continue boiling a short time.  Remove the cloth, wash it in clean water and dry it.  What color effects have you produced this time?
 
Can you dye with other natural coloring matters with or without a mordant?  Try the colors from butternut or black-walnut shucks, or the extract from chips of osage orange.
 
EXPERIMENT 571 - How to make e brown sulphur dye
Put five drops of glycerine in a dry test tube and add one measure of sulphur and one measure of sodium carbonate.  Heat the test tube over an alcohol or gas flame for several minutes and then allow the test tube to cool.
 
Now add a little water to the test tube and allow the test tube to stand for half an hour until the cake is loosened in the bottom of the tube. Now pour the contents of the tube into a glass of water and notice that the dye dissolves and the water is colored brown.
 
EXPERIMENT 572 - How to make a black sulphur dye 
Mix together on a piece of paper one measure of tannic acid, one measure of sodium carbonate and one measure of sulphur.  Put this mixture in a clean, dry test tube and heat the tube over an alcohol or gas flame for four or five minutes.
 
Now remove the tube from the flame and after it is cool fill the test tube half full of water and allow the test tube to stand for half an hour.  Now shake the contents of the tube thoroughly and then pour it into a glass three-quarters full of water. If any dye remains in the test tube add a little more water, shake again and pour it into the glass.  Notice the dark black color of the water produced by this dye.
 
EXPERIMENT 573 - How to make black logwood dye
Dissolve one measure of ferric ammonium sulphate in a test tube one-third full of water.
 
In another test tube half full of water put two measures of logwood and boil for four or five minutes until the solution is colored a bright red.  Pour this solution into the test tube containing the solution of ferric ammonium sulphate and notice the black colored solution which is formed.
 
EXPERIMENT 574 - How to make dark red logwood dye
Dissolve one measure of cobalt chloride in a test tube one-third full of water.  In another test tube half full of water put two measures of logwood and boil this solution for four or five minutes.  Pour this solution into the test tube containing the solution of cobalt chloride and notice the dark red solution which is formed.
 
EXPERIMENT 575 - How to make green logwood dye
Dissolve one measure of copper sulphate in a test tube one-third full of water.  
In another test tube half full of water put two measures of logwood and boil this solution for four or five minutes.  Pour this solution into the test tube containing the solution of copper sulphate and notice the green color which is formed.
 
EXPERIMENT 576 - How to make blue horse chestnut dye
Put several chips of the bark from a horse chestnut tree into a test tube half full of water and boil four or five minutes. Now add a little household ammonia and let boil again for two or three minutes.  Notice the blue colored solution which is formed.
GILBERT CHEMISTRY 169
 
EXPERIMENT 577 - Changing red logwood solution yellow, then blue
Boil two measures of logwood in a test tube half full of water for four or five minutes.  Then pour this solution into a test tube containing one measure of sodium bisulphate.  Notice that the solution turns from red to yellow in the presence of an acid.
 
Now add to this solution two or three measures of sodium carbonate and notice on shaking the color changes from yellow to reddish~blue or purple. Red logwood solution is yellow in the presence of an acid and blue in the presence of an alkali,
 
EXPERIMENT 578-Changing yellow turmeric solution brown
If you can obtain a little turmeric dissolve one measure in a test tube half full of water  by boiling the solution for three or four minutes. Then add one measure of sodium carbonate and notice that the solution turns brown.  Turmeric is yellow in the presnece of acids and brown in the presence of alkalies.
 
EXPERIMENT 579 - Changing red cochineal solution violet, then orange
Put one measure of cochineal in a test tube half full of water and boil until the solution is bright red.  Then add one measure of tartaric acid to this solution and shake the contents of the test tube.  Notice that the solution turns from red to orange.  Now add two measures of sodium carbonate and shake the contents of the tube again.  Notice that the  orange solution now turns violet.
 
Red cochineal solution is orange colored in the presence of an acid and violet in the presence of an alkali. 
 
EXPERIMENT 580 - How to dye cloth red
Put two measures of ferric ammonium sulphate in a test tube one-third full of water and shake the tube until all the solid is dissolved. Now place a small piece of cloth to be dyed in this solution and after it is thoroughly wet, remove the cloth and allow it to dry.
 
Now dissolve two measures of sodium sulphocyanate in a test tube one-third full of water and place in this solution the dry cloth which was treated with the ferric ammonium sulphate solution.  Notice that the cloth is dyed red.  Remove the cloth from the solution and allow it to dry.
 
EXPERIMENT 581 - How to dye cloth dark blue
Dissolve two measures of sodium ferrocyanide in a test tube one-third full of water and place in this solution a small piece of cloth to be dyed.  When the cloth is thoroughly wet, remove it and allow it to dry.
 
Now dissolve two measures of ferric ammonium sulphate in another test tube one-third full of water.  Place the dry cloth in this solution.  When the cloth is thoroughly wet, remove it and allow it to dry. This time the cloth is dyed a beautiful dark blue known as Prussian blue.
 
EXPERIMENT 582 - How to dye cloth a light blue
Dissolve three measures of sodium ferrocyanide in a test tube one-third full of water and place in this solution a small piece of cloth to be dyed.  When the cloth is thoroughly wet, remove it and allow it to dry.
 
Now dissolve two measures of ferrous ammonium sulphate in a test tube one-third full of water.  Place the cloth into this solution and shake the test tube a few times.  Remove the cloth and allow it to dry.  This time the cloth will be dyed a light blue, known as Turnbull's blue.
170 GILBERT CHEMISTRY
 
EXPERIMENT 583 - How to dye silk gray
Dissolve two measures of sodium bisulphate in a test tube half full of water.  In another test tube put two measures of logwood and boil the solution until it is colored bright red. Pour this red solution into the solution of sodium bisulphate.
 
Now place a small piece of white silk to be dyed in this solution and heat the solution to boiling. Remove the silk and notice that it is dyed gray.
 
EXPERIMENT 584 - How to dye cotton iron buff
Make a solution of ferric ammonium sulphate by dissolving two measures of the compound in a test tube one-third full of water. Place in this solution a small piece of cotton cloth to be dyed and shake the contents of the test tube thoroughly. Remove the cloth and allow it to dry.
 
Now dissolve two measures of sodium carbonate in a test tube one-third full of water and place the cloth in this solution. Shake the contents of the test tube thoroughly and then remove the cloth.  Wash the cloth with water and allow it to dry.  The cloth will be dyed an iron buff.  This color is produced by the precipitation of  iron oxide upon the fiber by the alkaline salt, sodium carbonate.
 
SPOT AND STAIN REMOVAL
 
Chemical treatment is often required in order to remove spots and stains from fabrics. To do this successfully, you need to know, not only what chemical will remove the stain, but how well the fabric will withstand the chemical action.  When the fabric is colored, the problem is still more complicated for the dyes may be attacked  by the chemical.  The following general rules may save you many mistakes.
 
1. If you use acid in cleaning cotton, be sure it is very thoroughly washed out before dyeing.
 
2. Do not use alkali on silk or wool.  If possible, avoid the use of water and clean with a dry-cleaning solvent such as carbon tetrachloride.  Many silks may be washed in water, but you should first be sure that they have been dyed with colors fast to washing.
 
3. Many spot removers act by bleaching with chlorine. Never use these on silk for chlorine damages silk. Chlorine is also very likely to attack dyestuffs.  If silk must be bleached, use a solution of hydrogen peroxide made slightly alkaline with sodium silicate.
 
EXPERIMENT 585-To remove grease from clothing
A grease stain which has been in clothing for some time can be removed by treating the stain with alcohol, gasoline or carbon tetrachloride.  Carbon tetrachloride is the best solvent to use, as it is non-inflammable, cheap and vaporizes quickly.  ln removing a grease stain in this way, always begin at the edge and work into the center, rubbing the stain thoroughly with a cloth containing some of the solvent.  This is a case of solution.  A fresh grease spot when removed in this way often leaves a ring on the clothing.  To remove a grease spot place a little tale or starch over and under the spot and warm the spot with an iron.  The talc will absorb the grease and can be easily brushed off afterwards.  Repeat the process until the spot is removed.  This is a case of absorption.
 
A grease spot may also be removed by rubbing neutral soap on the spot until a lather is obtained and then rinsing off with water.   This is a case of detergency.
 
EXPERIMENT 586-To remove paint from clothing  
If paint is fresh it is not difficult to remove.  First rub turpentine, lard, or linseed
GILBERT CHEMISTRY 171
 
oil into the stained spot.  Then clean it with carbon tetrachloride as in the experiment above.  
 
EXPERIMENT 587-To remove ink spots
First rub the spot lightly with a bleaching solution. This is made by dissolving four measures of calcium hypochlorite in a test tube half full of water.  This will change the spot to a yellow color. Then pour a little hydrogen dioxide on the spot and again rub lightly.  Notice that the spot is now entirely removed.  This is a case of bleaching.  This is a chlorine bleach and should not be used on silk and only for a short time on wool.
 
EXPERIMENT 588 - To remove iron rust
Obtain a small amount of oxalic acid and dissolve four measures in a test tube half full of water. Rub the spot with some of this solution and notice that the stain is removed.  Dilute hydrochloric acid can be used in place of the oxalic acid.  Remove the oxalic by washing with water.
 
EXPERIMENT 589 - How to remove acid spot
If acid is accidentally spilled on the clothing, pour a little ammonia on the spots and rub lightly with a cloth.  Wash the spot with water in order to remove the salts that are formed in the reaction.  This is a case of neutralization, the ammonia neutralizing the acid to form a salt.
 
EXPERIMENT 590 How to remove alkali from clothing
If caustic soda is accidentally spilled on the clothing pour some tartaric acid solution or vinegar on the spot and then wash the spot out with water. This is another case of neutralization.
 
EXPERIMENT 591 - How to remove grass stain
Grass stains may be removed by rubbing the spot with a little alcohol or carbon tetrachloride.
 
EXPERIMENT 592 - How to remove mildew 
Dissolve three measures of calcium hypochlorite in a test tube half full of water and rub the stain lightly with a little of this solution.  Remove the calcium hypochlorite by washing with water.
 
EXPERIMENT 593 - How to remove iodine stain 
Dissolve three or four measures of sodium thiosulphate in a test tube one-third full of water and rub some of this solution on the fabric stained with iodine.  Notice that the blue or brown stain is quickly removed.  Then wash the spot with water to remove the sodium thiosulphate.
 
TEXTILES AND AGRICULTURE

It is a far cry from woolen mittens worn by the country school boy, and a silk scarf adorning the costume of his sister, to a five thousand acre sheep ranch in Texas or Australia, and the primitive industry of reeling raw silk from cocoons in eastern China, but chemistry is constantly providing new and practical products from agricultural resources to provide pleasure, comfort and health in every corner of our country.  The boy, who today is performing his first experiments with a Gilbert Chemistry Set, may tomorrow be the chemist who will be making life happier and more secure for nearly every person in our land.
 
Several attempts have been made to develop silk culture in this country, but without financial success on account of the high labor cost. Agricultural experiments organized
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to promote this industry in this country have been inaugurated in the different states of the Union, from the Atlantic to the Pacific coasts.  At the present time an extensive effort is bein made to develop a raw silk industry in Southern California.  The worm can apparently be propagated wherever the mulberry tree can be grown successfully.
 
SOURCE OF WOOL
 
Wool comes from a sheep’s back. So does a lot of dirt and other materials picked up on his travels. He also exudes from the pores of his skin oily products which are generated by glands in his body. Only about one-half of the fleece is actual wool fibre.  Fifteen per cent is grease, 15 per cent salts, and 20 per cent clay and dirt.  Therein lies the reason why the woolen industry calls on the chemist to advise it how to prepare crude fleece for public use as clothing.  It is a long chemical story from crude sheep's fleece to a woolen blanket on your bed, to a suit of clothes, to a pair of warm woolen mittens, and to a dyed rug on the sitting room door of your home.
 
EXPERIMENT 594 - Wool scouring
Secure if you can a small quantity of wool fleece before it has been subjected to any scrubbing treatment. Examine it and try to clean it by scrubbing with different detergents.
 
EXPERIMENT 595 - Wool grease
Instead of scouring your fleece with detergents to remove dirt, soak it for several hours with some petroleum naphtha or ordinary gasoline. This will remove the valuable grease known in the drug trade as "lanolin." This wool fat is an important constituent of cosmetic preparations.  Finally apply treatment with detergents to remove dirt.  These two experiments will serve to reveal to you some of the difficulties facing the woolen manufacturer in preparing his product for public use.
 
EXPERIMENT 596 - Clothing
lt takes a sheep and a half to make a man a suit of clothes.  Test the fabric used in your shirt and stockings and determine which contains wool.
 
EXPERIMENT 597 - Shoddy 
What is the difference between the different forms of woolen cloth - worsteds, serges, flannel and shoddy?  Examine a piece of shoddy under your microscope.  What is there peculiar about its structure?
 
SOURCE OF COTTON
 
Cotton is a plant product and comes from the cotton plant. It is a cleaner commercial product than wool fleece and does not offer as many difficulties in purification.  This plant is cultivated in all parts of the temperate and torrid zones, and is the source of enormous industries spread over our globe. 
 
EXPERIMENT 598 - Cotton industries
Try to enumerate thirty commercial products which are manufactured from cotton.  Make a chart showing the industries producing these products.
 
EXPERIMENT 599 - Cotton plant  
Obtain if possible some raw cotton and examine it.  Who invented the cotton gin?  What is this machine used for?
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SOURCE OF SILK
 
Silk is an animal product and is produced by the silk worm known as Bombyx Mori.  This worm is cultivated and reared chiefly in China, Japan and Italy.  The silk worm feeds on the leaves of the mulberry tree, and stores up a liquid silk solution in his body.  After the worm has reached maturity it then exudes this silk solution in the form of a fine thread and weaves a cocoon.  This cocoon is made u chiefly of a protein called fibroin and this is the basis of natural silk.  Artificial silk, of which rayon is an example, is a modification of ordinary cotton.
 
EXPERIMENT 600 - Cocoons
Secure a silk cocoon and cut it into halves by means of a sharp knife.  Observe the dry chrysalis of the original worm encased in the cocoon.
 
EXPERIMENT 601 - Degumming
Take the severed cocoon and boil it for a long time in hot soap solution.   Wash with hot water and then dry the fiber and note its silky appearance.
 
EXAMINATION OF FABRICS WITH THE MICROSCOPE
 
EXPERIMENT 602 - Wool fiber
Under a microscope wool consists of regular cylindrical fibers covered with scales.  Make an examination of a wool fiber with your own microscope.
 
EXPERIMENT 603 - Cotton fiber
Cotton fiber looks like a collapsed rubber tube, twisted on its axis. Make an examination of a cotton fiber with your own microscope. 
 
CHEMICAL IDENTIFICATION OF TEXTILE FIBERS
 
In the home will usually be found some form of commercial lyes.  These consist essentially of sodium hydroxide and can be used for the following fabric alkali tests.  A tablespoonful of lye to a teacup of water will give a solution of sufficient strength for performing these fabric experiments calling for use of alkali.
 
EXPERIMENT 604 - Identification of wool
A fiber of wool, when burned, is consumed slowly, a ball-like end being formed.  The odor is characteristic of burning animal matter.
 
EXPERIMENT 605 - Solubility of wool in alkali
Wool protein is dissolved by being boiled with strong sodium hydroxide solution for a few minutes.  Add to an alkaline solution of wool a few drops of copper sulphate solution.  Black copper sulphide will be formed, showing the presence of sulphur in wool.
 
EXPERIMENT 606 - Identification of cotton
Burn a fiber of cotton and note that it burns quickly without giving any animal-like odor.  The odor resembles that of burning paper.
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EXPERIMENT 607 - Action of alkali on cotton
Boil a fiber of cotton with strong sodium hydroxide solution.  Note that unlike wool it will not dissolve.

EXPERIMENT 608 - Action of alkali on silk
Dissolve a fiber of silk in boiling sodium hydroxide solution; cool and then add three or four drops of copper sulphate solution. A lavender coloration will be produced.  This is characteristic of proteins which do not contain sulphur.
 
EXPERIMENT 609 - Action of alkali and copper sulphate on cotton
Boil a fiber of cotton with alkali; then cool and add three or four drops of copper sulphate.  No lavender or blue coloration will be produced.  Cotton does not respond to the test first, because it is not soluble in the sodium hydroxide solution, and secondly, because it is not a protein.
 
THE CHEMISTRY OF THE BODY
 
Man is dependent on the plant kingdom for his source of food. ln this way man utilizes indirectly the energy of the sun. Plants grow up, wither and fall to the ground.  They decompose largely into carbon dioxide and water vapor, which are  taken up by new plant life. The nitrogen is converted into nitrates by bacteria in the soil, and the mineral matter helps to form new plant life.

Sugars are formed in plant life by the condensation of formaldehyde which is produced by the action of carbon dioxide on water with the aid of sunlight.  The sugars are then changed into starch by plant ferments or enzymes and these starches are used by animals to support life.  In animals these starches are changed back into carbon dioxide and water and the whole process repeats itself.  Up to date, man has acquired through research a very extensive knowledge of the chemical changes taking place in this marvelous life cycle.
 
In the laboratory we have great difficulty in changing carbon dioxide into formaldehyde and formaldehyde into sugar.  In plant life this is done at relatively low temperature which is less than that of the body (98.6 degrees Fahrenheit or 38 degrees Centigrade).  This is accomplished by the action of the plant enzymes and is a very remarkable and important process.
 
In animal life we find enzymes similar to those in plant life.  Sugar (dextrose) for example, is changed into starch (glycogen) in the liver and this is later turned into dextrose again in the blood by the action of another enzyme.  The dextrose in the blood is converted by still further enzymic action into carbon dioxide and water vapor which are carried to the lungs and passed out on breathing.  This change takes places. in the muscle cells and furnishes the body heat.
 
The lean flesh or tissues of our bodies consists chiefly of protein. The fat is very similar to other animal fats. The bones consist chiefly of calcium phosphate and chrondrin which forms gelatin on boiling.  In old people there is more calcium phosphate present and less chrondrin than in younger people, consequently the bones of older people are apt to be more brittle.
 
The skin consists of toughened protein matter.  The hair and nails consist also of protein material and are called keratin.  Alkalies attack the skin, hair and nails because proteins are decomposed by alkali.  Mild acids, however, have little or no effect on these organisms.  The perspiration which comes from the skin contains water, fats, acids and a little urea.  We breathe to a very slight extent through the minute pores in the skin.  This seems to be an important and necessary process so that it is essential to
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keep these pores open by bathing, since they are continually closed by fat which condenses in the perspiration.

The blood, which is the most vital part of the body, is composed of water, containing in solution, protein material called fibrinogen, seroglobulin, seralbumin and saline water.  Also suspended in this solution are red and white corpuscles. Neutral salts when taken into the body are decomposed, the acid constituent usually hydrochloric acid from salt, going to the gastric juice in the stomach and the alkaline constituent going to the blood.  Therefore, the blood is normally alkaline.  When blood is exposed to the air it clots.  This is due to the fibrinogen in the blood changing to an insoluble compound called fibrin.  The blood usually contains about 0.1 per cent of dextrose.  The red corpuscles of the blood contain what is known as haemoglobin.  This is an enzyme containing iron.  It produces some of the very fundamental changes in the body in the same way that chlorophyll does in the plant.  This haemoglobin has the property of taking up oxygen from the lungs and later giving up this oxygen during the oxidation of the tissues.  During this oxidation heat and energy are formed.  The white corpuscles sometimes called leucocytes are really the policemen in the blood for they tend to ward off sickness by destroying the impurities in the blood such as bacteria.  When the number of bacteria becomes too great for these white corpuscles we become sick and then we have to resort to medicine to help the action of the white corpuscles.

A very important constituent of the brain and nerve cells is the substance known as lecithin.  This is a complex organic compound containing phosphorus.  Ordinarily the foods we eat contain small amounts of this substance, thereby furnishing the body with the necessary amount.

You may ask the question, Why is the blood normally alkaline?  This is easily explained by the fact that it is up to the blood to remove the acidic carbon dioxide gas from the body.  In an alkaline condition the blood can easily absorb these waste products of oxidation and in so doing forms sodium bicarbonate.  The sodium bicarbonate in the blood gives up carbon dioxide and water vapor in the lungs.  This leaves sodium carbonate which is the alkaline constituent of the blood and the blood is now ready to pass again through the body and take up more carbon dioxide.

The teeth differ from the other parts of the body in that they are more resistant to chemical action, namely, that of acids.  The mouth of a normal person is alkaline and in this state the teeth are well protected.  Decayed matter if allowed to cling to the teeth is converted into acids which slowly but effectually remove the enamel from the teeth and cause them to decay.  The enamel of the teeth is composed chiefly of calcium fluoride.  You can readily see, therefore, that it is very important to brush the teeth every day and the use of a mild antiseptic as a mouth wash is very effectual.
 
It is necessary to say at this time a few words in regard to body health.  There are several influences which tend to keep up a healthy normal body. These are exercise, fresh air, cheerfulness, cleanliness, sunlight, pure food and pure water.  The relationship between chemistry and exercise may be shown if we consider that many chemical reactions take place much more rapidly and with better results if the solution in which the reaction is taking place is heated or stirred continually.  Just so in the body. By exercising the body the blood moves faster, the stomach digests our food better,  we breathe much more efficiently and as a consequence the waste products of the body are more effectually eliminated and we feel much better.
 
Sunlight has several effects on the body. It is a powerful germicide and will kill many organisms which are the cause of disease.  It also acts as a blood stimulator.  You probably have noticed how red the body becomes in the summer time when exposed to the sun's rays.-
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Cleanliness is a very important contribution toward health.  Dirt is a very good medium or culture for bacteria, so that it is quite necessary to keep the body clean.  We have always spoken of the importance of keeping the pores of the skin open so that impurities can come out in the form of perspiration and that pores may breathe in a certain amount of fresh air. Chemistry has contributed toward this influence on the health of the body by furnishing such substances as borax, soap, soda, ammonia, antiseptics and synthetic remedies.
 
Pure fresh water is a very important factor in everyday life.  Natural waters contain small amounts of mineral salts, principally sodium chloride. These are not injurious to the health but rather beneficial.  Waters, however, are apt sometimes to contain bacteria which may be very injurious to the health.  If a water is suspected as containing bacteria it should be boiled.  On a commercial scale water is purified by several processes, namely treating the water with ozone, bleachin powder, chlorine, ultra-violet light or by distillation.  Any of these methods are good if used under the right conditions.
 
The subject of fresh air is an old one, but one which a great many people disregard.  It is very important that the lungs obtain the normal amount of oxygen necessary in the oxidation processes which take place in the body. The effect of poisonous gases when breathed into the lungs was very ably demonstrated during the great war.  Impurities in the air such as poisonous gases, etc., have a very remarkable affinity for the blood.  They react with the blood to form much more stable compounds than oxygen does.  Consequently the blood cannot take up the normal amount of oxygen required in the body, and as a result the blood becomes congested. In the case of extreme poisoning the lungs become so congested that we are unable to breathe further, and death follows.  In a poorly ventilated room the carbon dioxide given off from the lungs soon becomes in excess of the oxygen present in the room, with the result that we become drowsy or sleepy. This effect seems to be due to a lowering of the oxygen content in the room and also to a rise in temperature caused by the body heat.
 
Cheerfulness is not directly related to chemistry but is mentioned here because of the influence it has on the health of the body. A person who is cheerful, particularly during the time of eating, is apt to be less troubled with indigestion than a person who is constantly worrying.  Loss of appetite is quite often due to just this thing.  Indigestion and loss of appetite are controlled to a large degree by the nerves, which are apt to break down in a person who is not cheerful.
 
The truth of the old saying that an apple a day keeps the doctor away is now vouched for by science. Apples contain vitamin C, which has been found necessary and valuable in promoting health and protection from diseases like scurvy.  All nutrition authorities now report that apples, while they do not contain as much of this vitamin as tomatoes or oranges, do supply an important amount of it, particularly if eaten raw, skin and all.
 
Let us try a few chemical tests to see if we can learn something about the body.
 
EXPERIMENT 610 - How to test for sugar in urine 
The excretion of urine from a healthy person should be free from sugar.  If sugar is found in the urine it is an indication that the liver is not functioning properly and the person has what is known as diabetes.
 
Put three measures of cream of tartar baking powder in a test tube half full of water.  After the reaction stops add one measure of copper sulphate and shake the contents of the tube thoroughly.  Now add four measures of sodium carbonate and four measures of calcium oxide.  Shake the test tube again thoroughly and filter the contents of the tube, catching the liquid in another test tube.  This clear liquid is known as Fehling's solution.
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Now to a test tube one-third full of this solution add four or five drops of urine and heat the test tube over an alcohol flame nearly to boiling.  Now remove the tube from the flame and see if a red precipitate has formed in the test tube.  A red precipitate formed in this way is a test for sugar in the urine.  The sugar reduces the copper hydroxide formed in the reaction of red cuprous oxide.  By this test it is also possible to determine the quantity of sugar in the urine.

Repeat this experiment, using four or five drops of a sugar solution in place of the urine.  The sugar solution is made by dissolving three or four measures of sugar in a test tube one-third full of water.  Notice the red precipitate of cuprous oxide which is formed by the action of the sugar upon Fehling's solution.

EXPERIMENT 611 - How to test for albumin in urine
The presence of albumin may be detected in urine as follows:

Heat a test tube one-third full of the urine to be tested over an alcohol flame with constant shaking.  Do not heat above 175 degrees.  This can be told by removing the test tube from the flame occasionally and feeling of the test tube with the hand.  When the test tube is too hot to hold in the hand the temperature of the urine is above the temperature required.  Do not heat the urine to boiling.  Now remove the test tube from the flame and allow it to cool.  Examine the contents of the test tube.  If a precipitate separates out the urine contains albumin.

Repeat this experiment, using a test tube one-third full of the white of an egg in place of the urine.  Notice that a gelatinous precipitate settles out. This is due to the coagulation or precipitation of the albuminous material contained in the white of the egg.

Albumin in the urine indicates that the stomach is not working properly, that the albumins are not changed during the process of digestion. They enter the blood in these forms and are passed out in the urine through the kidneys.
 
EXPERIMENT 612 - How to test for proteins in urine
Dissolve three measures of sodium carbonate and three measures of calcium oxide in a test tube one-third full of water.  Put the thumb over the mouth of the test tube and shake the contents of the tube thoroughly.  Allow the test tube to stand until the solid materials settle to the bottom.  Now pour the clear liquid into another test tube.  This is a strong solution of sodium hydroxide.

Now dissolve one measure of copper sulphate in a test tube one-third full of water.

To a test tube one-quarter full of the urine to be tested add the sodium hydroxide solution prepared above.  Shake the contents of the tube thoroughly and then add two drops of copper sulphate solution. The formation of a violet color on shaking indicates the presence of proteins in the urine.  The purple color becomes deeper on heating the solution to boiling.  This reaction is known as the Biuret Test for proteins.
 
EXPERIMENT 613 - Testing urine for acidity 
Drop a small piece of blue litmus paper in a test tube one-third full of urine and notice that the litmus paper turns red.  This proves that urine is generally acidic.  This is due to the presence of sodium dihydrogen phosphate in the urine.  The acidity of the urine depends upon the kinds of food taken into the body.  Vegetable foods tend to decrease the acid content and even render the urine alkaline.

EXPERIMENT 614 - Testing urine for ammonia
Put five measures of calcium oxide in a test tube one-third full of urine and heat the mixture over a flame for several minutes.  Remove the test tube from the flame and smell cautiously at the mouth of the tube. Do you recognize the odor of ammonia?  Ammonia occurs in urine chiefly in the form of organic compounds known as urea and creatinine.
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EXPERIMENT 615 - Testing urine for phosphate
Dissolve one measure of calcium chloride in a test tube one-quarter full of water.

Add a little of this solution to a test tube one-third full of urine and notice the formation of a white precipitate.  If the urine is alkaline the precipitate may be due to a mixture of calcium phosphate and calcium carbonate.  When urine is alkaline it contains, besides small amounts of ammonia, the carbonates of soda and ammonia.
 
EXPERIMENT 616 - How to test for acid mouth
Moisten a small piece of blue litmus paper with the tongue and see if the litmus paper turns red.  If it does the mouth is acid. Acid mouth is usually caused by an upset stomach or by decayed teeth.  Normally the mouth should be neutral or only slightly alkaline.
 
THE CHEMISTRY OF PLANTS - AGRICULTURE

As our knowledge of the chemistry of the processes of living organisms - animals and plants - increases it becomes increasingly difficult to define the boundaries between the animate (living organisms) and inanimate (inorganic or non-living.)  The significance of this statement will be apparent to any intelligent boy if he will only stop to consider the dependence of our civilization on the successful practice of agriculture.  The primitive source of the food of man is the soil, and consequently the successful practice of agricultural science is necessary if man is to secure food for his existence.  The farmer occupies, therefore, a most important place in human economy.  The energy which is necessary to promote the different chemical changes involved in animal and plant growth is derived from the sun.  Deprived of this source of energy, plants would not be able to grow, agriculture would be destroyed, and man would die.
 
THE CHEMISTRY OF FERTILIZERS - FARMING

Did you know that chemistry plays such an important part in farming and in the fertilization of soil?  No doubt you have often seen the farmer cover his soil in the Spring with manure or other forms of fertilizers and later work them into his soil.  You probably asked the question, why are these fertilizers put into the soil, and found that they make crops grow better.  That is true, the crops do grow better.  But why is this so?  By repeated experiments it has been found out that there are certain substances which are very essential to plant growth.  We have already learned how plant compounds, such as starch, are built up in the plant by means of carbon dioxide and moisture in the air with the aid of the sun's rays. On the other hand there are other important substances which are taken up by the plant in the soil to form complex compounds.  These are potassium, nitrogen and phosphoric acid.  These substances must be introduced into the soil in the form of their soluble compounds as they are taken up by the plant roots by means of absorption.
 
Nature plays s a very important part in the formation of nitrogenous substances in the soil.  You probably do not know that in most fertile soils there exists millions of bacteria which have the property of converting decayed nitrogenous organic matter into nitrates which are taken up by the plants.  Now it is very important in farming to see that the soil is kept in a condition whereby these bacteria are able to thrive in order to keep the soil fertile.  Soils which contain large amounts of decayed organic matter are kept in a moist condition so that the air does not get at them are quite often apt to be acidic. The nitrate forming bacteria are not able to live in soils which are acid so that it is very important to see that these acids are destroyed. Acid soils also render other fertilizing substances, such as phosphates, insoluble or in a condition such that
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the plant is unable to absorb them in the ordinary process of plant growth.  This acidic condition of the soil is generally destroyed by neutralization of the acids with lime.



In the ordinary process of farming, since the plants are continually removing the nitrogen, potassium and phosphorus compounds from the soil, it is necessary to replenish these substances with fertilizing material. Now the amounts and kinds of fertilizer to be put into a certain grade of soil depends upon the condition of the soil and kinds of crops to be raised. One class of plants will require more phosphorus than another class.  Many formulas have been worked out including the kinds and amounts of fertilizing substances to be used for different kinds of plants.

Soils are fertilized in four ways, namely, by decayed vegetable matter, by rotation of crops, by animal manure and by artificial or commercial fertilizers.

Decayed vegetable matter such as leaves, grass, etc., is often worked into the soil as a natural fertilizer, but since they contain only small amounts of essential fertilizing substances, their use alone would be inadequate.
 
The second method of fertilization, namely, the rotation of crops is widely used in farming and consists in planting fertile land one season with  wheat or other crops and the following season with cow-peas or alfalfa.  These latter plants have the property of converting nitrogen from the air into soluble nitrates which are restored to the soil to take the place of that used up by the corn, wheat and other crops in the preceding season.  The conversion of the air into nitrates is accomplished by certain germs or bacteria which occur in tubercles or swellings on the roots of clover, cow-peas. and alfalfa plants.

Natural or animal manures are used exclusively as fertilizing materials as they contain large amounts of nitrogen compounds.  They also tend to keep the soils loose so that the air can penetrate them,  Guano, cow and sheep dung are important natural manures containing relatively large amounts of nitrogen.  Guano is the excrement of sea-birds and is found off the coast of Peru.  Guano is rich in phosphorus, nitrogen and potash.

Artificial fertilizers are used very widely today and several important industries are involved in their manufacture.  These are chemical compounds or substances that are
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rich in nitrogen, phosphorus and potassium.  Phosphorus is used in these fertilizers in the form of its soluble compound such as calcium acid phosphate.  Potassium is used principally in the form of potassium chloride, potassium sulphate and potassium carbonate, while nitrogen is used in the form of ammonium nitrate and sodium nitrate.  The commercial fertilizers which are put out on the market are complete fertilizers, such as dissolved potash and phosphates, wood ashes, ground bones, dissolved bones tankage, dry ground fish, nitrate of soda, dried blood, cottonseed meal, linseed meal and castor pomace.
 
One of the important problems of the science of agriculture is to find out which of the elements that occur in plants and animals are necessary for their growth. Hitherto the farmer has been taught that only ten chemical elements are necessary for the growth and normal support of his crops,  It has, however, been a well-known fact among agricultural chemists that a far greater number of chemical elements than ten occur in small amounts in fertile soils, and also in the ashes of plants that have been grown under natural conditions.  The elements which have been regarded as the only ones essential for the growth of plants are the following: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, and iron.  It was perfectly natural that in the early days of agriculture these elements which occurred in the largest amounts would receive the first attention by agricultural chemists. However, with the development of new and modern methods of chemistry and with greater refinement in methods of research, it was not unreasonable to expect that a very large number of the chemical elements which have been regarded as non-essential would finally prove to be very important factors in plant growth.  This has really proven to be the case.  It is now known that the element, manganese, for example, is a very essential plant food.  It has been shown that plants will assimilate manganese compounds from the soil. It now also seems probable that manganese actually exists in small quantities in all living organisms, and has important functions that have hitherto been unrecognized.  All the facts to date show that manganese is an important and necessary factor in the synthesis of the green chlorophyll of plants, and experiments have already been carried out which show that no other one of the common elements - iron, copper zinc, boron, or arsenic - will replace manganese. Heretofore, it has been believed that iron and magnesium were chiefly concerned in the synthesis of plant chlorophyll.  lt has now been shown by recent workers in agricultural science that manganese plays a role of importance equal to that of iron in the synthesis of chlorophyll, and that both of these elements are indispensable for the formation of chlorophyll in plants.
 
EXPERIMENT 617 - Nitrogen forming bacteria
Pull up a clover or alfalfa plant and examine the roots. Notice that along the roots there are numerous small swellings  (Figure 36.)  These swellings are called tubercles and if these were crushed and examined under a powerful microscope you would find millions of small living bacteria in them.  These are the bacteria which convert the nitrogen from the air into soluble nitrates which are furnished to the soil and later taken up by other plants.
 
EXPERIMENT 618 - To show the effect of carbon dioxide on plant life
Procure two Mason quart jars and place about two inches of damp earth in each.  Now plant two or three peas or beans in each jar exactly under the same conditions.  Allow the jars to stand until the beans begin to sprout. Then fill one jar with carbon dioxide gas. The carbon dioxide gas is made by putting two spooafuls of baking soda or sodium bicarbonate in a third empty quart jar and adding a little vinegar or a solution of tartaric acid. After the reaction has gone on for several moments pour the gas
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