The Science Notebook
Gilbert Chemistry - Part 6

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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  In addition, much of the information contained in this book about chemistry and other subjects is outdated and inaccurate.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 101- 120


GILBERT CHEMISTRY 101
 
EXPERIMENT 226 - Pharaoh's serpents
Mix two parts potassium dichromate, (this can be secured in a drug store), one part of potassium nitrate and one part of sugar. The ingredients must be powdered separately and then mixed. Small paper cones can be made and filled with the compound which has been moistened either with alcohol or water. When dry light at the top.  As the cone burns "snakes" will form.
 
EXPERIMENT 227 - How to make snakes
These snakes are sold around the Fourth of July as fireworks. They are made very easily by mixing up four Gilbert measures of sugar, two measures of sulphur and two of cobalt chloride. Place in a spoon and heat over a candle. The mass will melt and then it will swell up in size. It is many times the size of the original mass. By mixing with alcohol and making into moulds and then allowing to dry you will be able make quite a stable compound.
 
EXPERIMENT 228 - Red flame from sawdust
Boil some sawdust or woodshavings in a cup of water containing a teaspoonful of potassium nitrate.  When 1t is dry it will burn with a white-yellow flame, sizzling as it burns.  Add some strontium nitrate to the potassium nitrate solution and it will burn with a red flame.
 
EXPERIMENT 229 - An aurora borealis
For this phenomenal experiment prepare a mixture of the following substances on an old tin pan: one measure of strontium nitrate, two measures of potassium nitrate, one measure of powdered charcoal, one measure of sulphur, one measure of powdered zinc, one measure of powdered magnesium and one measure of powdered iron.  Do not rub or grind the mixture. Set the pan in some place where sparks from the mixture will not damage anything.  Now ignite the mixture with a match or fuse and notice that the mixture will burn with different colored lights and at the same time produce showers of bright sparks.
 
The sparks are caused by the oxidation of the different metals in the mixture by potassium nitrate.
 
Obtain a soda water straw and, closing one end by folding it over, fill it with a mixture of the above substances.  Place the straw containing the mixture in a test tube and going out doors into the open, light the open end of the straw. Notice the beautiful effect produced by the burning mixture.
 
COLOR IN FIREWORKS
 
The bright reds, the greens and other colors produced in fireworks on the Fourth of July depend on the presence of the salt of a metal which has the property of imparting a particular color to a flame. In order to impart color, the salt must be volatile, in order for it to serve in this way. The beautiful red of Roman candles, sky rockets, are produced by salts of lithium or salts of strontium. Barium compounds are among the most common ingredients producing green effects in fireworks. Fireworks also serve very practical purposes outside the celebration of the Fourth of July. On railroad trains, for instance, a device known as the "fusee" is carried. This is a red flare which the brakeman places at the rear of a train that is stalled, or is used to warn the engineer of an approaching train.  In shipping, aviation, in military activities, rockets and flares are used for signals.

102 GILBERT CHEMISTRY
 
ALUMINUM, ZINC, MAGNESIUM 
 
These are three very important metals and find wide application in industry.
 
Aluminum is a very important metal because it is very malleable, is easily cast, is tenacious, and more rigid than the same weight of other metals. Its uses are many.  It is used for common household aluminum ware. It is used extensively in the manufacture of airplanes on account of its lightness and durability. Recently it has been used to construct the gondolas of the stratosphere balloons. Aluminum is also used as a conductor in electric power lines.
 
Aluminum forms valuable alloys with steel or magnesium.
 
The compounds of aluminum are important. The silicates are used extensively in manufacture of cement, brick, tile, earthenware, pottery and porcelain ware.  Several valuable gems contain aluminum. The ruby, sapphire and topaz are transparent crystals of aluminum oxide, containing small amounts of certain metallic oxide which impart the color.
 
The alums, which are double salts containing aluminum sulphate, are used as mordants in dyeing and printing. Because of its acid reaction in water, alum is used in some baking powders.
 
EXPERIMENT 230 - Colored aluminum lake
Put two measures of cochineal in a test tube half full of water, boil over the flame.  Now add one measure of aluminum sulphate and shake until it is all dissolved.  Dissolve one measure of sodium carbonate in another test tube 1/3 full of water and add to the first solution. Notice the red precipitate. This is aluminum hydroxide carrying with it the red cochineal. This process is used in dyeing and in clarifying water.
 
EXPERIMENT 231 - Action of sodium carbonate on aluminum sulphate
Dissolve one measure of aluminum sulphate in a test tube 1/3 full of  water.  In another test tube 1/3 full of water add one measure of sodium carbonate and shake until dissolved.  Now mix the two solutions and notice the formation of a gelatinous precipitate. This precipitate is aluminum hydroxide. Aluminum carbonate has has never been prepared, because it is a salt of a very weak acid and a weak base. Consequently it immediately hydrolyzes completely to form aluminum hydroxide, carbon dioxide and water. The gas given off in the reaction is carbon dioxide gas. 
 
Alum baking powder or cream of tartar substitute, as it sometimes comes on the market, consists of sodium bicarbonate, starch and potassium alum. The starch is used to keep the materials dry. 
 
Zinc is used in batteries and as a coating for other metals to, protect them from the oxygen of the air. Galvanized iron is made by dipping iron into molten zinc and allowing to cool. Zinc forms several important alloys. 
 
Zinc dissolves readily in both acids and alkalis producing hydrogen and a zinc salt.  Zinc also combines readily with certain other elements as oxygen and sulphur.
 
EXPERIMENT 232 - Action of zine on alkalis
 
To a test tube half full of sodium hydroxide, prepared as directed in experiment 202, add one measure of powdered zinc. Warm, if necessary, to start the reaction.  Notice the gas bubbling off . This is hydrogen.
 
Magnesium occurs abundantly in nature as the carbonate.  Metallic magnesium is very important commercially because of its extreme lightness and strength.  It is now a rival of aluminum in construction demanding a light metal.  Many of the large trucks used for transporting new automobiles are constructed of a magnesium alloy, "Dow metal," which is being extensively used. 

GILBERT CHEMISTRY 103
 
When ignited in air magnesium burns with a brilliant white light.  For this reason the powdered  metal, mixed with potassium chlorate (or potassium nitrate) is used as a flashlight powder in photography, as well as fireworks and signal flares.
 
The well-known milk of magnesia is magnesium hydroxide and epsom salts is magnesium sulphate.
 
EXPERIMENT 233 - How to make a white flashlight powder
Mix together on an old pan one measure of powdered magnesium and one measure of potassium nitrate.  Do not rub or grind the mixture. Now place one measure of sulphur on top of the mixture and carefully light the sulphur. The sulphur will burn and suddenly the mixture will flash, giving off a very brilliant light.
 
Try this same experiment, leaving out the sulphur and using a fuse made by soaking a piece of string in a strong solution of potassium nitrate and allowing the string to dry.   In setting off the mixture with a fuse, place the mixture on one end of the fuse and light the other end with a match.
.  
EXPERIMENT 234 - How to make a red flashlight powder
Repeat experiment 233, using one measure of strontium nitrate in place of the potassium nitrate.  Notice the brilliant red light produced when the mixture is ignited.
 
235-How to make a green flashlight powder
Repeat experiment 233, using the following proportions of substances: one measure of potassium nitrate, two measures of powdered magnesium, one measure of boric acid, and one measure of sulphur.  Notice this time that a bright green flash is produced.
 
Do not allow any of the above flashlight mixtures to remain in the air too long, as some of the salts take up water from the air and therefore will not ignite quickly.
 
EXPERIMENT  236 - Making sparklers
Mix together on a sheet of paper one measure of potassium nitrate and two measures of powdered magnesium.  Do not rub or grind the mixture. Now melt some paraffin in your spoon and dip a match into the liquid paraffin until it is well coated. Remove the match from the paraffin and after a few seconds roll it in the mixture of magnesium and potassium nitrate. When you have a good covering of the mixture on the match, allow the match to dry thoroughly for several minutes. Now light the end of the match and notice that it will burn and give off bright sparks. The 4th of July sparklers are prepared in a manner similar to this.
 
THERMITE
 
EXPERIMENT 237 - Thermite fusion
This well-known experiment on thermite can always be depended upon to arouse an intense enthusiasm for science. The experiment should not be undertaken, however, without the advice and direction of an older person, and should not be conducted in surroundings where there is danger of fire and injury to property.  It is a perfectly safe experiment to perform, but the necessary chemicals are not supplied in sufficient quantity in your set, and must be purchased in the market.  For the demonstration, it is first necessary to prepare a plaster of Paris cone.  This is made by coating the inside of a large funnel with vaseline. A large paper cone is placed inside, and it is also coated with vaseline.
 
A hollow plaster of Paris cone is now made, using the prepared funnel as a mold.  Before the plaster sets, a hole is made in the bottom of the cone.   When the plaster is hard, it can be very easily slipped from the funnel.  
104 GILBERT CHEMISTRY
 
The cone is placed in a large ring on a ringstand, at the base of which is a pan [?] of sand. A piece of paper is stuffed into the opening at the bottom of the cone so as to prevent the ignition mixture from dropping out. The cone is then filled with the mixture of aluminum powder and iron oxide. Other oxides, of course, may be substituted. To insure a good yield of molten metal, a liberal number of iron brads is added to the mixture. 
 
On top of the mixture a very small heap of an oxidizing agent is placed.  A piece of magnesium ribbon is then stuck into the oxidizer, the cone is covered with a sheet of asbestos, containing a small hole for the magnesium strip, and the magnesium ribbon is ignited.
 
This demonstration is most dazzling and impressive when shown in a darkened room.
 
SILICATES
 
EXPERIMENT 238 - Silicic acid
Put 1/2 inch of water glass in a test tube and add water until the tube is one-quarter full. Shake to mix the liquids.
 
In another test tube put four measures of sodium bisulphate and fill the tube one-third full of water. Shake until the solid is completely dissolved.
 
Pour the sodium bisulphate solution into the water glass. A jelly-like precipitate will form, and in a few minutes all the liquid in the tube will become solid.
 
EXPERIMENT 239-Sodium silicate (water glass)
Paint a thin film of water glass on a sheet of paper and let it dry for 15 or 20 minutes. Note the smooth transparent glass-like film which results.
 
Paste together two sheets of paper or two blocks of wood, using water glass as the adhesive. You will find that it makes an exceptionally strong paste and it is often used for this purpose.

EXPERIMENT 240 - Strontium silicate
Dissolve two measures of strontium chloride in half a test tube of water and add two or three drops of water glass.

A bulky white precipitate will form and upon shaking the test tube the precipitate will fill the whole tube. `
 
EXPERIMENT 241 - Zinc silicate
Place a small piece of zinc metal and two measures of sodium bisulphate in a test tube. Fill the tube half full of water, heat the solution for a moment and wait until some of the zinc dissolves. Now hold the tube in a glass of cold water for a moment or two until it becomes cool.
 
Add to the solution of zinc sulphate thus formed two or three drops of water glass.  Zinc silicate will be formed.
 
EXPERIMENT 242 - Aluminum silicate
Place two measures of aluminum sulphate in a test tube and fill the tube half full of water, shake to completely dissolve the solid.  Now add two or three drops of water glass and note the thick white precipitate of aluminum silicate which is immediately formed.
 
EXPERIMENT 243 - Nickel silicate
Place two measures of nickel ammonium sulphate in a test tube and fill the tube half full of water. Warm the solution for a few moments to completely dissolve the

GILBERT CHEMISTRY 105

solid, and immerse the tube in cold water to cool it again.

Now add two or three drops of water glass to the solution of nickel ammonium sulphate and you will get a beautiful green precipitate of nickel silicate.

EXPERIMENT 244 - Ferrous silicate
Dissolve two measures of ferrous ammonium sulphate in a test tube half full of water.  To this solution add two or three drops of water glass and a thick precipitate of ferrous silicate will be formed.

EXPERIMENT 245 - Ferric silicate
Dissolve two measures of ferric ammonium sulphate in a test tube half full of water and add two or three drops of water glass. A very pretty reddish-brown precipitate of ferric silicate will be formed.

EXPERIMENT 246 - Tin silicate
Put one measure of sodium bisulphate, one measure of ammonium chloride, and a small piece of tin metal into a test tube. Add five or six drops of water and heat the liquid, allowing it to boil for two or three minutes. Pour the clear solution into another clean test tube and add water until the tube is one-quarter full.

Now add two or three drops of water glass and in a few moments a thick white precipitate of tin silicate will form.

EXPERIMENT 247 - Chromium silicate
Dissolve two measures of chrome alum in a test tube full of water. Add two or three drops of water glass and a beautiful thick green precipitate of chromium silicate forms immediately.

EXPERIMENT 248 - Cobalt silicate
Dissolve one measure of cobalt chloride in half a test tube of water and add two or three drops of water glass. 

In this case a beautiful blue precipitate of cobalt silicate is formed.

EXPERIMENT 249 - Copper silicate
Place two  measures of sodium bisulphate and one measure of copper sulphate in a test tube and fill the tube half full of water. Heat the liquid for a few moments until a clear blue solution of copper sulphate is obtained. Add to the copper sulphate solution two or three drops of water glass and examine the blue precipitate of copper silicate which is formed.

EXPERIMENT 250 - Manganese silicate
Place two  measures of manganese sulphate in a test tube half full of water and heat the liquid for a few moments to completely dissolve the solid.

Now add to this solution two or three drops of water glass. A pale pink precipitate of manganese silicate will be formed.

EXPERIMENT 251 - Magnesium silicate
Dissolve two measures of magnesium sulphate in a test tube half full of water.  Add to this solution two or three drops of water glass. A white precipitate of magnesium silicate will be formed.

EXPERIMENT 252 - Calcium silicate
Put three measures of calcium chloride in a test tube half full of water, and shake until the solid is dissolved. Now add two or three drops of water glass and you will get a white precipitate of calcium silicate.

106 GILBERT CHEMISTRY

FERROCYANIDES

EXPERIMENT 253 - Zinc ferrocyanide
Dissolve two measures of sodium ferrocyanide in a test tube half full of water.  In another test tube put a small piece of zinc metal and two measures of sodium bisulphate. Fill the test tube 1/4 full of water and shake until the solids are dissolved.  Now add a few drops of the sodium ferrocyanide solution from the first test tube and a white precipitate of zinc ferrocyanide will be formed.

EXPERIMENT 254 - Aluminum ferrocyanide
Dissolve one measure of aluminum sulphate in a test tube half full of water.  Add a few drops of the solution of sodium ferrocyanide prepared before and a light brown precipitate of aluminum ferrocyanide will be formed. If this precipitate appears blue it shows that there is a trace of iron in the aluminum sulphate.

EXPERIMENT 255 - Nickel ferrocyanide
Dissolve one measure of nickel ammonium sulphate in a test tube half full of water.  Add a few drops of the solution of sodium ferrocyanide prepared before and a light green precipitate of nickel ferrocyanide will result.

EXPERIMENT 256 - Ferrous ferrocyanide
Dissolve one measure of ferrous ammonium sulphate in a test tube half full of water and add to this solution two or three drops of sodium ferrocyanide solution.  The resulting bluish white precipitate which forms is the same thing as Turnbull's blue.

EXPERIMENT 257 - Ferric ferrocyanide
Dissolve one measure of ferric ammonium sulphate in a test tube half full of water and add a few drops of sodium ferrocyanide solution. The deep blue color which results is called Prussian Blue, which is ferric ferrocyanide.

EXPERIMENT 258 - Manganese ferrocyanide
Dissolve one measure of manganese sulphate in a test tube half full of water.  When you add to this solution a few drops of sodium ferrocyanide solution a white precipitate of manganese ferrocyanide is formed.

EXPERIMENT 259 - Cobalt ferrocyanide
Dissolve one measure of cobalt chloride in a test tube half full of water.  Add to this solution a few drops of sodium ferrocyanide solution and a pretty green precipitate of cobalt ferrocyanide is formed.

EXPERIMENT 260 - Chromium ferrocyanide
Dissolve one measure of chrome alum in a test tube 1/4 full of water. To this add a few drops of sodium ferrocyanide solution and a deep green color will appear, due to the formation of chromium ferrocyanide. Notice that in this case the color is not in the form of a precipitate as the chromium ferrocyanide is soluble.

EXPERIMENT 261 - Tin ferrocyanide
Put one measure of sodium bisulphate, one measure of ammonium chloride, and a small piece of tin metal in a test tube and add five or six drops of water.   Heat the solution, allowing it to boil for two or three minutes to dissolve some of the tin.  Now pour the clear solution into another test tube and add a few drops of the clear solution into another test tube and add a few drops of sodium ferrocyanide solution. Note the light bluish green precipitate of tin ferrocyanide which is formed.

[107]

PART III
Organic Chemistry and Its Commercial Application to the Industries


CARBON

Organic chemistry is based on our knowledge of the properties and reactions of compounds of the element, carbon. This element is found in nature in the free condition in several forms. The diamond is practically pure carbon, while ordinary coal and graphite contain small percentages of other substances besides carbon as mineral matter.  Naturally occurring compounds of carbon are of wide occurrence in nature and are found in the form of gases, liquids or oils and solids. Carbon dioxide is the most familiar gaseous compound of carbon. Manufactured illuminating gas, natural gases from wells and petroleum are all composed chiefly of organic compounds of carbon and hydrogen.

The carbonates, especially calcium carbonate, constitute a very large proportion of the natural rocks and some form of mineral carbonate are found in most localities.  The building stone - marble - is a very pure form of calcium carbonate. Carbon constitutes a large percentage of all living organisms, both plant and animal, and is represented in such organic products as proteins, fats, sugars and natural oils. All products of these types are widely utilized by man as food and for the manufacture of useful commercial products. At the present time more than 300,000 organic compounds are known, and the possibilities of new creations as the science of organic chemistry is developed are unlimited. Of all the elements occurring in nature, carbon is the one which is most commonly associated with life itself. Our present world could not exist without this element.

Coke is a modified form of impure carbon, and is used as a fuel in operating steam boilers, and also in smelting processes for refining ores. It is made by heating bituminous, or as it is more commonly known, soft coal until all volatile products in the coal have been expelled. This heating process is conducted without excess of air, and is carried out out on a commercial scale in large ovens. The volatile or gaseous products are refined and constitute the raw materials for the manufacture of illuminating gas and low boiling hydrocarbons like benzene.

Every boy and girl is familiar with ordinary charcoal. This is a form of carbon produced by the destructive distillation of organic substances such as wood and sugar, and even bones of animals. By destructive distillation is meant heating without access to air as in the manufacture of illuminating gas. The quality of wood charcoal obtained is dependent on the kind of wood which is subjected to destructive distillation. It is known, for example, that the destructive distillation of cocoanut shells is productive of a very efficient form of absorbent carbon meeting the exacting requirements of the gas mask.  If air was admitted during the distillation process, the charcoal and gaseous products would be burned up completely with formation of carbon dioxide gas and water.

Another form of carbon is graphite. This is the black substance which forms the core of lead pencils. lt is sometimes referred to as lead, but this is not correct. It is not lead, but a modified form of carbon, and can be made by subjecting carbon to a very intense heat.  At about 4000į C. carbon vaporizes, and this vapor on condensing forms graphite.  Graphite is used in the manufacture of crucibles, as a lubricant, as a

108  GILBERT CHEMISTRY

protective covering for metals such as stove polish, and in the manufacture of lead pencils.

Lamp black, an amorphous form of carbon, finds wide application in the trades.  It is used in rubber as a toughening agent; in printers' ink as a pigment; in paints, stove polishes and lacquers as a pigment; on typewriter ribbons and and carbon papers as a black coloring matter. Bone black is an amorphous carbon produced by destructive distillation of bones. It is used as a deodorizing and decolorizing agent.

THE MANUFACTURE OF ILLUMINATING GAS



Cylindrical ovens of Fire clay (B-Figure 31) are filled automatically with soft coal.  These ovens are then closed tightly to prevent entrance of air.  Under these ovens is a hot fire (A). The heat decomposes the coal into gases, liquids and coke.  The gases contain impurities such as hydrogen sulphide, carbon dioxide, ammonia, tar, benzol, toloul and water. These impurities are removed before the gases are passed into receiving tanks.

Then first step towards purification of the gases is as follows: The gases pass from the oven through a pipe and bubble through running cold water contained in the lower half of a large pipe (C).  Here coke dust (carbon), tar oils and ammonia are removed. 

Second, the gases are then passed through an arrangement (D) which consists of several hundred feet of pipe. This acts as a condenser and cools the gas down to ordinary temperature and condenses the liquid products of the distillation.

Third, the gases pass from the condenser through a "scrubber" where they are washed and cleaned. The scrubber (EE) is a large iron tank filled with coke, crushed rock, wood, and scraps of tin, the object being to expose a large surface to the gas.  A spray of water is introduced at the top of the scrubber and the material filling it is thus kept moist. The remainder of the tar and ammonia salts are here removed and the gasses pass on to the purifier.

Fourth, the gases are passed through the "purifier" (FF), a rectangular box filled with layers of quick lime, which absorbs  water, carbon dioxide and hydrogen sulphide. 

After the moisture is removed, the gases, which now consist of hydrogen, nitrogen, marsh gas, olefiant gas, acetylene and carbon monoxide are delivered immediately into the large gas tanks (G). These tanks are constructed in telescopic fashion so

GILBERT CHEMISTRY 109

that the quantity of gas regulates and controls the size of the tank. From  the tank it is pumped through gas mains to the homes of the consumers. (H) is the entrance pipe.  (I) is the exit pipe. (K) is the flue or chimney for the fire.

You may have noticed at times the tremendous flame which shoots up in the vicinity of gas tanks. This is especially noticeable at night. The cause of this seems to be mysterious.  It is exceedingly simple. When live steam is passed over white hot coke away from air, in an oven for instance, water gas is formed.  Water gas cannot be used for lighting purposes alone; it is mixed with the coal gas. Water gas consists of a mixture of hydrogen and carbon monoxide and is produced by the action of steam on hot carbon.

After the steam has been passed into the ovens for a time new coke must be must be added: in other words, the ovens must be charged regularly.  Before emptying the ovens, valves shut off the gas connection of the oven with the rest of the plant. ln the ovens there still remains a good deal of gas. This gas must be removed before the ovens are emptied of the coke. The quickest and best way is to burn it away.  This is done and the gas disappears in a tremendous flame. Thus the "aurora borealis" of the city is a mystery no more.

EXPERIMENT 262 - Preparation of charcoal - pyro-ligneous acid
Break up a few toothpicks or pieces of wood and place them in the bottom of a test tube.  Now put a piece of moistened blue litmus paper over the mouth of the test tube and heat over an alcohol lamp or gas flame. Notice that the paper turns red, proving that an acid is evolved. This acid is called pyro-ligneous acid and is essentially acetic. Acetic acid is also present in vinegar. Here it is formed in the process  fermentation resulting by the action of bacteria on sugar.

Now insert the peforated cork with delivery tube, continue heating and and light the gas that comes off. Notice that it will burn. This gas is similar to that obtained from the distillation of coal.

When no more gas is evolved, allow the tube to cool, then empty the contents of the test tube on paper. This is charcoal and is practically pure carbon.

When green pine (or green cedar wood) is distilled, turpentine and tar oils are derived from it. The turpentine is the volatile oil, that is, it passes off as a vapor. The tar oils are the heavy resinous oils, brown in color, such as you may see at the bottom of your test tube.

To summarize, when coal is heated without admission of air, coal gas, ammonia and coal tar are obtained. The is used for lighting and heating. The ammonia which is derived is purified and finds many uses. From the coal tar are derived intermediates from which aniline dyes, disinfectants such as carbolic acid, high explosives and many other valuable products are manufactured.

It can be seen, therefore, that enormous industries are based upon this process of heating wood and especially coal without admission of air.

THE SMOKING OF HAMS AND MEATS

Pyro-ligneous acid is contained in the smoke of smoke houses where hams and other foods are cured. ln the pioneer days of New England agriculture, a smoke house was a common feature of the farmerís equipment. Usually this was built out of doors, but in many cases installed in the attic of the farm house.  It is due to the aseptic action of this acid in the smoke that pork and beef products are preserved.  The probable action of the gradual deposition of pyro-ligneous acid upon a ham is to gradually kill all the bacteria or germs which are the cause of decay.  The acid also imparts that distinctive taste which is characteristic of smoked food. 

110 GILBERT CHEMISTRY

Meats can be cured over night, while in the smokehouse several days are required.  This quick curing is a rather new method and is not practiced except experimentally.  The ham is painted with pyro-ligneous acid, which seeps into the meat.  It has been declared that the quick cured ham is as edible as the slow cured ham and keeps just as well.

EXPERIMENT 263 - Decolorizing properties of charcoal
Make a solution of potassium permanganate by dissolving a crystal in a test tube half full of water. Shake until all is dissolved and the solution is  colored purple. 

Now put into this solution three measures of powdered charcoal and closing the mouth of the tube with the thumb, shake vigorously for two or three minutes.  Now filter this solution in the funnel and notice the color of the liquid that runs through.  It is nearly colorless, showing that charcoal has the property of a absorbing colors from certain substances.

Repeat this experiment with different colored solutions and notice which of the colors are absorbed by charcoal.

EXPERIMENT 264 - Deodorizing properties of charcoal
Prepare some hydrogen sulphide water as shown in a previous experiment and notice the odor. To this solution add three measures of powdered charcoal, close the mouth of the test tube with your thumb and shake the test tube for minutes. Now filter this solution and smell the liquid which runs through.  Notice that the odor has been removed by the charcoal.
'
EXPERIMENT 265 - Absorbing properties of charcoal
Dissolve a small piece of quinine pill about the size of a pin head in a test tube half full of water and taste the solution. Notice that it is bitter.

Now add three measures of powdered charcoal, close the mouth of the test tube with your thumb and shake for three or four minutes. Filter this solution and taste a little of the liquid which runs through. Notice that the bitter taste is gone.

Charcoal then removes colors, odors and tastes from certain solutions.

ABSORBENT CHARCOAL

EXPERIMENT 256-Abeorbing coloring matter with charcoal
Put about 1/8 measure of cochineal in a test tube 1/4 full of water.  Warm the tube for a few moments until the cochineal dissolves, forming red solution.

Now put two measures of powdered charcoal into the cochineal solution and close the mouth of the test tube with your thumb and shake three or four minutes.  Filter the solution after you have shaken it thoroughly in order to separate the charcoal and you will find that the color will be a great deal lighter than it was in the original solution.  By repeating this process several times it will be possible to take practically all of the color out of this solution.

Try this experiment on logwood solution, or solutions containing dyes, or on any other colored liquids.

EXPERIMENT 257 - Decolorizing vinegar
Fill a test tube one-quarter full of vinegar which has a brownish or yellow color.  Add two measures of charcoal and shake with the solution for four or five minutes.  Now separate the charcoal by filtering, and you will find that the color of the vinegar is lighter. The vinegar can be made almost colorless by repeating this several times.

GILBERT CHEMISTRY 111
 
EXPERIMENT 268 - Absorbing bitter taste with charcoal
If you can obtain a small amount of quinine you will find that charcoal will absorb the bitter taste. Fill a test tube one-quarter full of water and add a very small amount of quinine, about the size of an ordinary pinhead. Shake this with the water and taste a drop of the the solution and notice the bitter taste.
 
EXPERIMENT 269 - Absorbent charcoal from ground cocoanut shells
Grind up a piece of dry cocoanut shell and thoroughly bake the material in a copper oven.  This should be thoroughly carbonized by this treatment. After baking then grind the particles of dried shell to a powder by rubbing in a mortar.  Test the efficiency of this powder as a decolorizing and absorbing agent.
 
EXPERIMENT 270 - Absorbent charcoal from butternut shells 
Crack some butternuts and eat the meat of the nuts. Then take the shells and thoroughly crush them and finally carbonize by heating in a copper oven. After this baking then grind to a powder in a mortar. Test the efficiency of this powder as a decolorizing agent and absorbing agent.
 
EXPERIMENT 271 - Preparation of absorbent charcoal from hickory nut shells
Follow the same directions as given for Experiment 270.
 
EXPERIMENT 272 - Preparation of absorbent charcoal from white birch wood
Carbonize some small pieces of white birch wood in a copper oven. After this baking, then grind to a powder in a mortar. Test the efficiency of this powder as a decolorizing agent and absorbing agent.
 
EXPERIMENT 273 - Preparation of absorbent charcoal from pine wood
Follow same directions as given for Experiment 272.
 
EXPERIMENT 274 - Preparation of absorbent charcoal from maple wood
Follow same directions as given for Experiment 272.
 
EXPERIMENT 275 - Preparation of absorbent charcoal from chestnut wood
Follow same directions as given for Experiment 272.
 
EXPERIMENT 276 - Surface tension and the rubber band
Float a thin rubber band on a dish of water and touch the water inside the band with a wire or tooth pick which has been dipped into oil. The band will snap out, forming a circle. Now apply oil to the water outside of the band and the band will again resume its original shape.
 
This experiment illustrates the effect of surface tension which tends to make liquids assume those forms which expose the least surface for a given volume.
 
EXPERIMENT 277 - Changing the specific gravity of charcoal
Wood charcoal floats in water. Tie a weight on a piece of charcoal with a thread so that it will sink and place it in a test tube one-quarter full of water.  Boil the water several minutes, then remove the weight from the charcoal, and you will find that it no longer floats. This is due to the fact that the air was driven away from the pores of the charcoal by boiling.  This experiment illustrates why wood becomes waterlogged  and does not float. 

112 GILBERT CHEMISTRY
 
CARBON DIOXIDE OR CARBONIC ACID GAS
 
When carbon and any combustible compound of carbon is burned, the carbon is converted into carbon dioxide as the final product of oxidation. This is a gas heavier than air, and is the most commonly known of all carbon derivatives. While it does not support combustion, it does serve a valuable purpose in both human and plant economy. In the plant kingdom, carbon dioxide is absorbed from the air through the cells of the leaves and furnishes the source of carbon for building up plant tissues. The transformation of carbon dioxide in the plant is brought about under the agency of the sun's rays and the influence of the green chlorophyll of the leaves of the plant.
 
While carbon monoxide is poisonous, carbon dioxide is a harmless gas. It is a waste product thrown off by the lungs during respiration. lt has been proved that carbon dioxide in the lungs is responsible for stimulating the respiratory center in the process of breathing. The deep and rapid breathing from extensive violent physical  exercise, like baseball and football, is not due directly to the need of oxygen, but rather to the need of eliminating carbon dioxide from the lungs. The increase of the carbon dioxide production is a measure of the work being done under violent exercise. Use is made of carbon dioxide for administration to patients suffering from hiccoughs.  Also to increase the breathing rate after an anethesia and even after carbon monoxide poisoning.  While carbon dioxide is not ordinarily considered poisonous, it can, however, be responsible for death, because it will not support combustion.  The ordinary procedure of testing the air in a mine or a deep well, or any building or inclosed place having poor ventilation, with a lighted candle has proved to be very wise in many cases. 
 
MEDICAL USES OF CARBON DIOXIDE
 
Ordinarily we think of carbon dioxide as being associated with fire extinguishers, and for this reason it is sometimes hard for most of us to appreciate that carbon dioxide can play an important part of a life-saver and alleviator of pain. We now know that carbon dioxide stimulates respiration and serves as a means of increasing the rate of breathing.  Advantage is taken of this effect in certain cases where breathing is suspended, as during asphyxiation, physical shock, and partial drowning.  Machines for administering mixtures of oxygen and carbon dioxide have proved more capable of giving relief in these types of cases than those which use oxygen alone.  The breath stimulating effect of carbon dioxide, and the ventilation produced by oxygen has saved many lives. Carbon dioxide as an aid in the removal or the anesthetic when it is longer needed, is a general hospital practice.
 
CARBONATES OF METALS
 
The carbonates of many metals are insoluble in water and can be precipitated from solutions by means of a soluble carbonate such as sodium carbonate.  In the following experiments you will obtain many colors.  Filter off your insoluble precipitates and note the color of the carbonate salts.
 
EXPERIMENT 278 - Strontium carbonate
Dissolve one measure of strontium chloride in a test tube half full of water.  In another test tube one-quarter full of water dissolve one measure of sodium carbonate.  Now add some of the sodium carbonate solution to the strontium chloride solution and a heavy white precipitate of strontium carbonate is obtained.

GILBERT CHEMISTRY 113
 
EXPERIMENT 279 - Nickel carbonate
Dissolve one measure of nickel ammonium sulphate in a test tube half full of water.  Dissolve one measure of sodium carbonate in another test tube 1/4 full of water.  Now add the sodium carbonate solution a little at a time to the solution of nickel ammonium sulphate and a thick light green precipitate of nickel carbonate will be formed.  
 
EXPERIMENT 280 - Zinc carbonate
Put a small piece of zinc metal in a test tube, add one measure of sodium bisulphate and fill the tube 1/4 full of water. Warm this solution and let it stand for three or four minutes so that some of the zinc metal will dissolve.
 
Now prepare a solution of one measure of sodium carbonate in a test tube 1/4 full of water and add some of this solution to the zinc solution. A white precipitate of zinc carbonate will be formed which gradually settles to the bottom of the tube.
 
EXPERIMENT 281 - Aluminum carbonate
Dissolve one measure of sodium carbonate in a test tube 1/4 full of water.  Dissolve one measure of aluminum sulphate in another test tube 1/4 full of water.  Add the sodium carbonate solution to the aluminum sulphate solution a little at a time.  Notice that at first an effervescence takes place and then a gelatinous precipitate of basic aluminum carbonate is formed.
 
EXPERIMENT 282 - Chromium carbonate
Dissolve one measure of chrome alum in a test tube half full of water. Add a few drops of sodium carbonate solution as before, and notice that a bluish green precipitate of chromium carbonate forms.
 
EXPERIMENT 283 - Ferrous carbonate
Dissolve one  measure of ferrous ammonium sulphate in a test tube half full of water.  To this solution add a few drops of a solution of one measure of sodium carbonate in a test tube 1/4 full of water.  A greenish precipitate of ferrous carbonate will form.
 
EXPERIMENT 284 - Cobalt carbonate
Repeat the experiment using one measure of cobalt chloride in place of the ferrous ammonium sulphate.
 
EXPERIMENT 285 - Calcium carbonate
Put one measure of calcium chloride in a test tube half full of water.  Shake thoroughly and then add a few drops of sodium carbonate solution prepared as in the preceding experiment.  A white precipitate will be formed which is calcium carbonate.
  
EXPERIMENT 286 - Copper carbonate
Place one measure of azurite, which can be purchased at your drug store, and one measure of sodium bisulphate in a test tube. Fill the tube half full of water and shake for a few moments until the solution becomes perfectly clear.  Now add a few drops of sodium carbonate solution prepared as before, and a very pretty precipitate of copper carbonate will be formed.
 
EXPERIMENT 287 - Manganese carbonate
Dissolve one  measure of manganese sulphate in a test tube half full of water.  Add a few drops of sodium carbonate solution prepared as before, and you will obtain an while precipitate of manganese carbonate.

114 GILBERT CHEMISTRY
 
EXPERIMENT 288 - Magnesium carbonate
Add one measure of magnesium sulphate to a test tube half full of water and dissolve by shaking.  Now add a few drops of sodium carbonate solution, as before, and a white precipitate of magnesium carbonate will be formed.
 
CARBON MONOXIDE
 
While carbon dioxide is a harmless gas, this member of the carbon family is a violent poison. It is formed when carbon is burned with a diminished supply of oxygen. The gas burns with a blue flame being convened into carbon dioxide.
 
Several thousand people are killed each year by carbon monoxide gas, which constitutes a small proportion of the gases expelled through the exhaust pipe of an automobile.
 
With the return of cold weather, the spectre of carbon monoxide poisoning haunts every automobile driver. Unless humanity has exercised an excess of caution, we may expect occasional news items about persons warming up their motors in closed garages, being overcome by this insidious gas. Carbon monoxide is a product of imperfect combustion.  When a fuel is burned under perfect conditions, carbon monoxide is not produced. The products of perfect combustion are carbon dioxide and water. Ideal combustion conditions are difficult to realize. Certainly not in the very best of our automobiles. An analysis of the exhaust gases of an average automobile shows about 7% of carbon monoxide. ln a certain experiment a dog was left in the driverís seat of an automobile in a closed garage, with the engine running slowly. In twenty minutes the dog was unconscious. Had a man been in the dog's place, the result would probably have been the same.  Carbon monoxide overcomes its victim with no warning.  The first symptom is a severe pain in the back of the head, but if the concentration is high, the victim may lose consciousness before he can act on this warning.  This condition may or may not be preceded by such warnings as headache, dizziness or nausea.  Small doses may have no other effect than to cause severe headache, but a heavy gassing is a serious matter.  Convalescents from carbon monoxide poisoning should be kept in bed even when they protest that they are all right.  To avoid carbon monoxide poisoning it needs no more than good ventilation in the garage.  Carbon monoxide is lighter than air, and vanishes immediately through an open window or door. A doctor should be called immediately for a person overcome by the gas.  An automobile driven by a driver under the influence of carbon monoxide constitutes a hazard to the public safety on the highway equal in seriousness to that of another car equipped with faulty brakes.  It has been found that an automobile, following too closely behind another, particularly in heavy traffic, may pick up a sufficient quantity of the exhaust gas from the preceding car to result in a dangerous mixture within the second automobile, leading to carbon monoxide poisoning.
 
ETHYL GAS
 
Every automobile driver is familiar today with the trade term - "ethyl gas."  This is an organic compound containing lead which bestows on gasoline the favorable properties characteristic of this reagent (tetraethyl lead). It is a practical anti-knock substance. When ethyl gasoline is used, it tones down the explosions in the cylinders of gas engines, and pushes the cylinder more gently than in the case when ordinary gasoline is used. Tetraethyl lead is a dangerous substance, and warnings, therefore, accompany its use.  At every filling station there are warnings posted to the effect that ethyl gas should not be spilled upon the hands or used for cleaning purposes.  If ordinary precautions are followed, tetraethyl gasoline presents little danger during use.

GILBERT CHEMISTRY 115
 
EXPERIMENT 289 - Preparation of carbon dioxide - (effervescence)
make a solution of sodium bicarbonate by shaking up a test tube 1/3 full of water containing two measures of sodium bicarbonate. ln another test tube make a solution of tartaric acid by shaking up a test tube 1/3 full of water containing two measures of tartaric acid. Now pour the tartaric acid solution into the solution of sodium
bicarbonate.
 
Notice the violent effervescence due to the chemical action and liberation of carbon dioxide gas.  You will notice that it has no odor.  This is the same gas that you see bubbling out of soda-water.
 
EXPERIMENT 290 - Vinegar and baking soda
Obtain some very strong cider vinegar, the stronger the better, and place about 3 cc. in a test tube.  Then drop into the vinegar a small measure of baking soda. What gas is given off?  Test for it.
 
EXPERIMENT 291 - Vinegar and oyster shells
Repeat the above experiment using a piece of oyster shell. Pulverize the shell in a mortar before adding it to the vinegar. Warm the solution and test the gas given off.
 
EXPERIMENT 292 - Vinegar and painters whiting
Repeat the above experiment using some painter's whiting.   What is the composition of ordinary whiting?
 
EXPERIMENT 293 - Vinegar and chalk
Repeat the above experiment using some powdered chalk or crayon from your school room blackboard.
 
EXPERIMENT 294 - Vinegar and marble
Repeat the above experiment with some pulverized marble.
 
EXPERIMENT 295 - Vinegar and tooth powder
Repeat the above experiment with a good quality of dental tooth powder. What constituent of tooth powder causes the reaction?
 
EXPERIMENT 296 - Vinegar and old mortar
Repeat the above experiment using some old mortar removed from the walls of an old brick building. Note the evolution of carbonic acid gas.
 
EXPERIMENT 297 - Vinegar and Portland cement
Repeat the above experiment using some pure Portland cement.
 
EXPERIMENT 298 - Carbon dioxide is heavier than air, and will not burn
Light a candle and set it firmly on a board by sticking it to a little melted wax from the flame of the candle. (Figure 32).
 
Now put one-half teaspoonful of sodium bicarbonate or common baking soda in a glass and add some vinegar or a solution of tartaric acid to the glass.  A violent reaction takes place with evolution of carbon dioxide gas. 
 
Now pour the gas in the glass on to the flame just as though you were pouring water out of the glass, taking care not to spill any of the acid out of the glass.  Notice that the flame goes out, proving that carbon dioxide is heavier than air and will settle to the earth and also that it will not burn.

116 GILBERT CHEMISTRY
 



 
EXPERIMENT 299 - Chemistry of the flame
Examine closely an alcohol lamp flame or candle flame and observe that it consists essentially of three cones. (Figure 53).  First a dark cone just around the wick: second, a yellow cone which produces! light; and third, a transparent cone of heat around the outside.
 
The dark cone of the flame consists of unburned gases which are given off from the wick of the candle.  The paraffin is melted by the heat and drawn into the wick by capillary action.  In the wick the paraffin is converted a gas by the heat of the flame. To prove this, hold one  end of a hollow glass tube in the flame just over the wick.  Now apply a flame to the other end of the tube and it takes fire.  The gas in this cone is relatively cool, for if a match stick is placed in it that portion of the stick which was in the dark cone will not burn as soon as the portion passing through the sides of the flame.
 
The second or yellow cone of the flame consists of particles of carbon that have been heated to white heat so that they glow brightly.
 
Hold a cold spoon or glass rod in this cone for a minute and notice that it is covered with a black deposit of carbon called lampblack, thus proving that this cone consists of small particles of carbon.  The cold spoon chilled the flame, thereby causing the carbon particles to be deposited. Lampblack is made upon this principle on a manufacturing scale. 
 
The third or outer cone of the flame consists of the gases formed by the complete burning of the carbon particles to carbon dioxide gas. This is the hottest portion of the flame, and whenever heating a liquid in a test tube, for example, it is important in order to obtain the highest heat possible and to prevent the deposit of soot, to hold the test tube at the tip of the luminous or light-giving part of the flame.

GILBERT CHEMISTRY 117



EXPERIMENT 300 - Carbon dioxide from a burning candle
Make some lime water by putting  two measures of calcium oxide in a test tube half of water and shaking well for three or four minutes. Allow this solution to stand until clear, then pour the clear liquid into another test tube. You now have a clear solution of lime water or calcium hydroxide.
 
Now hold a wide mouthed bottle or fruit jar over a candle flame as shown in Figure 34 so that the burning gases from the flame may enter the mouth of the bottle.  After allowing the gases to enter the bottle for about a minute, close the mouth of the bottle with the palm of the hand, and, inverting the bottle, pour the lime water into it.  Again put the palm over the mouth of the bottle and shake for a moment. Notice that the lime water becomes turbid or milky. This turbidity is due to a white precipitate or calcium carbonate formed by the action of carbon dioxide on calcium hydroxide.

EXPERIMENT 301 - The structure of a flame - A gas factory
If you will look closely at a candle flame you will see that it consists of three parts.

First, a dark zone just around the wick. 

Second, a bright yellow zone which gives the light.

118 GILBERT CHEMISTRY
 
Third a transparent zone of heat around the outside.
 
The first or inner zone consists of unburned gas given off from the wick of the candle. The melted grease is drawn up by a capillary action into the wick and is there converted into gas by the heat of the flame. With care a portion of this gas can be drawn off through a tube.

Hold one end of the glass tube in the flame and directly over the wick. Hold the tube slanting upwards so that the other end is out at the side and a little above the flame.  If held correctly smoke will come from the end of the tube and can be lighted with a match. 

That it is relatively cool inside of the flame can be shown by thrusting a match stick into this zone for a few seconds. The portion of the stick which was held in the dark zone will not be burned as soon as that portion passing through the sides of the flame.
 
EXPERIMENT 302 - The structure of flame - Manufacturing lampblack
The second or bright yellow zone of the flame contains particles of carbon heated to a white heat so that they glow brightly. The carbon is formed by the action of the heat on the gas of the inner zone. 
 
The presence of this carbon can be shown by holding a cold spoon or piece of glass tubing in the flame for about a minute. You will notice that when you take it out it is covered with a black deposit of lampblack or soot which is one form of carbon.   The cold spoon chills the flame and prevents the carbon from being completely burned.

Lampblack is made on a large scale in just this way except that natural gas is burned instead of candles and the cooling is done by means of iron pipes with water circulating through them.
 
The third or outside zone of the flame consists of the gases formed by the complete burning of the carbon particles. lf you will hold the cold spoon in the outer zone you will find that it gets very hot but that no soot or only a very small amount will be deposited.  This zone is above the luminous one.

EXPERIMENT 303-Carbon dioxide in the breath



Make up a solution of lime water as previously directed. 

Now take a hollow glass tube, put one end into the test tube containing the lime water and allow your breath to bubble through the lime water. (Figure 35)  Notice that very soon the water becomes turbid and after a short while a white precipitate is formed.  This precipitate is calcium carbonate and is formed by the action of carbon dioxide in the breath upon lime water or calcium hydroxide.

TANNIN AND ITS APPLICATIONS.
 
The raw skin obtained from an animal must be chemically treated to become useful as leather or fur, otherwise it becomes shriveled and horny when dry, or, if wet, it is attacked by bacteria which causes putrefaction and decay.

GILBERT CHEMISTRY 119

The chemical treatment is called tanning, and the chemical which combines with the raw skin to change it to leather is called a tannin.

There are many tannins from different sources which are alike only in their ability to convert raw skin into leather. Simple treatment with salts like alum and with oils may suffice for furs. Chromium compounds are used in chrome tannage, and complex compounds produced by the action of formaldehyde and sulphuric acid on phenols are known as synthetic tannins or "syntans" but have their use limited by cost.  The principle tannins are extracted from trees and plants, sometimes from the bark, sometimes from wood, leaves, or fruit. The bark of oak and hemlock and the wood of the chestnut tree have long been used, but one of our most important sources of tannin is the wood of the quebracho tree which grows in South America. Your chemical set contains a supply of purified tannin called tannic acid. 

Tannin is unpleasant to taste for it puckers the mouth, as anyone knows who has tasted a green persimmon. If you follow the directions given below you can easily test various plant materials to see if they contain tannin. Possibly you may discover a  valuable new source of tannin in some ordinary weed.
 
The tanning of skins to make leather is too long a process to describe here but there are many other applications of tannin which make interesting experiments.

EXPERIMENT 304 - Testing for tannin
Weigh out one spoonful of ordinary gelatin such as is used in the kitchen for making desserts.  Also weigh out seven spoonfuls of sodium chloride (common salt) and dissolve them together in 10 test tubes of water. This is your test solution.  It spoils quickly just as moist raw skins do unless you add a drop or two of a suitable antiseptic such as carbolic acid.

Now to see what happens when tannin is present, make up a solution of one measure of tannic acid in one test tube of water. Fill a test tube about one-third full with the gelatin solution and add the tannin solution drop by drop. The cloudiness which develops shows that the tannin has made the gelatin insoluble in water. This is not only a very sensitive test for tannin, but it shows what happens when tannin changes raw skin substances to leather.

Raw skin is chemically very similar to gelatin, so when it is soaked in water containing tannin a similar precipitation takes place within the structures of the piece of skin, converting it from a soft jelly-like consistency to a firm tough texture.

EXPERIMENT 305 - Another test for tannin
Make up a test solution by dissolving one measure of ferric ammonium sulphate in 10cc. of water. Add a drop of this to a one-quarter test tube of your tannin solution.  The black color which forms is an indication that tannin is present. Try it on a more dilute tannin solution.  Is the test very sensitive?  Some tannins produce a dark green color with iron instead of black.
 
You will find elsewhere in this book how you can make use of this color change to produce ink and perform various mysterious tricks.

EXPERIMENT 306 - Test for tannin in tea
Drop a pinch of dry tea in a test tube, cover it with water, and heat nearly to boiling.  Now carefully pour off the clear tea extract from the leaves and add a drop or two to a little of the gelatin test solution. Also add a drop or two of ferric alum solution to some of the tea extract in another test tube. Do you find any tannin in tea?

EXPERIMENT 307 - Tannin from oak bark
Obtain some oak bark and cut it up into fine shavings.  Put some of these shavings in a test tube half full of water and boil for two or three minutes. Allow the test tube

120 GILBERT CHEMISTRY
 
to cool and pour the liquid into another test tube. Test as above for tannin in the extract.
 
EXPERIMENTS 308, 309, 310, 311, 312 - Tannin from hemlock bark, chestnut bark, chestnut wood, sumac leaves, acorns
Follow the directions of the previous experiment (307) with these materials.  Many other common trees and plants contain tannin in varying amounts. Try extracting tannin from some of your native trees, shrubs, and weeds. The tannin content varies in different parts of the same tree. Usually it is present in higher percentage in the bark, but frequently the leaves, fruits or nuts, and the heartwood are rich in tannin.

Tannin is important in other ways besides its use in making leather. Oak timbers owe much of their resistance to rotting to their tannin content. Many shrubs are not eaten by grazing animals, except as a last resort to keep from starving, because of the taste of the tannin in the leaves. Some tannin is used in the textile industry to assist in dyeing. This use is illustrated by experiments in another part of your handbook.

Tannin has long been used in medicine, and this application is increasing greatly since it has been discovered that it is especially valuable for treating burns.
 
EXPERIMENT 313 - Making a tannic acid solution for burns
Dissolve about 2 measures of tannic acid in four test tubes of water.  For small burns, saturate a small pad of cotton or gauze with this solution and hold it in place over the burn with a loose bandage. Very large and severe burns are treated by  bathing in the tannin solution or applying the solution as a spray.
 
In an emergency if your supply of tannic acid is used up, you can extract enough tannin from tea, as described above in experiment 506. Simply extract the tea leaves with hot water, using plenty of tea, and use the clear water extract to treat the burn.
 
PAINTS, LACQUERS, AND WATER COLORS
 
In all of these you will find a solid substance furnishing body and color with a liquid called the vehicle. It is the nature of the vehicle which makes the chief difference between paints, lacquers, and water colors.

In paints the vehicle is an oil such as linseed oil which is capable of combining with oxygen of the air to become hardened to a tough film. When such an oil has been mixed with a solid such as lead carbonate or zinc oxide it produces a good weather-resisting paint. In this case the paint will be white, but suitable coloring matters called lakes and pigments may be added to give any desired color. 

If these solid colors are ground up with water containing a little glue or gum to make them stick, water colors are produced. White wash and calsomine are common examples. These are not usually weatherproof enough to be used outdoors, but are popular for inexpensive painting of inside walls.

Lacquers may be considered a kind of varnish, differing from the older types of varnishes and paints in that the vehicle does not consist of an oil which dries by oxidation, but is some form of gum or resin dissolved in a mixture of solvents, which evaporate to deposit the gum, together with any pigments and coloring matter, in a tough film. The lacquers may be made very quick~drying by using solvents which evaporate quickly, but if they dry too quickly the film is brittle and does not hold well to any surface it is to cover. To remedy this, a small proportion of a substance called a plasticizer is added. This is a comparatively non-volatile substance like castor


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