The Science Notebook
Gilbert Chemistry - Part 3

  Home   Terms of Use   Safety  Contact Us   Experiment Pages   Downloads   Supplies   Useful Links!


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  In addition, much of the information contained in this book about chemistry and other subjects is outdated and inaccurate.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 41- 60

GILBERT CHEMISTRY 41

MEASURING LIQUIDS OR SOLUTIONS



The medicine dropper (Figure 16) is a very useful piece of apparatus for measuring out several drops of a liquid or solution. The dropper is filled by pressing on the dropper bulb and inserting the end of the dropper into the solution.  On relieving the pressure, the dropper is filled with the solution.

Always wash out the dropper with water several times before using it with different solutions.

GLASS BLOWING

Only a few simple operations can be undertaken in glass blowing unless you have special equipment.  You should know how to cut glass tubing and rods, how to fire polish the cut ends, and how to make very simple bends.

EXPERIMENT 11 - To cut small glass tubing and rods
To cut a rod or tube, make a scratch by one (and only one) stroke of a sharp triangular file at the place where it is to be cut. Now hold the tube in both hands with the thumbs together and pressing gently on the glass on the opposite side from the scratch.  It should break very easily if the scratch was properly made.

EXPERIMENT 12 - Fire polishing glass
The edges will be very sharp after a fresh cut, but by holding the glass over the flame of the alcohol lamp so that only the sharp edge is in the hot part of the flame you will be able to soften the glass until a smooth round edge forms. This is called fire polishing.

EXPERIMENT 13 - To bend glass
Cautiously heat the glass in the flame of the alcohol lamp, turning it continuously so as to be sure you heat it evenly all the way around. When it has softened, remove the glass from the flame and bend it a little. Return it to the flame and soften another portion of the glass just beyond the portion you softened first. Bend the glass a little more. Repeat, if necessary, until the glass has been bent to the desired angle.

If you have a gas burner you can heat a larger portion of the glass at once and you may be able to make the complete bend with only one heating.

You may find that you can often devise useful a apparatus from materials that you find around the house. For instance, tumblers and jelly glasses are just as useful as beakers, provided you never try to heat them.  You can make larger jars by cutting off the necks of bottles or jugs.

EXPERIMENT 14 - To cut a glass jug in two
First make a short file scratch at the right height and tie around the jug at this place a string soaked in alcohol. Light the string with a match and rotate the jug slowly in a horizontal position while it burns. The glass usually cracks around under the string.  If it does not, you may help it by touching the hot glass with a drop of cold water.

[42]

PART II

Inorganic Chemistry and Its Commercial Application to the Industries

MATTER IN CHEMISTRY


Matter may be either an inorganic or an organic substance. Before one begins to think in the terms of chemistry, he ought to know first the difference between materials and immaterial things. Material things are matter and matter is something that occupies space; something that takes up room. It can he either inorganic or organic material. Immaterial things are not matter; for example, a thought is not matter; it does not take up room; it has neither length, breadth, nor thickness; you cannot feel, taste or see it. A good example of a material thing is air enveloping the earth; this has weight and it takes up room. Water also is matter. In the form of a small raindrop, it has size, form, and weight; it occupies space. It is a material thing

KINDS OF MATTER

Matter is found in different forms such as gas or vapor, liquid and solid, and many of the same substances of matter may be made to assume all the three different forms.  Water, for example, is of common occurrence in nature as a liquid, but if the temperature falls low enough, as in winter weather, water is chilled finally becomes a solid which we recognize as ice. On the other hand if the temperature rises high enough, the water becomes invisible and turns into a gaseous state, which we utilize in the form of steam as a source of power in the steam engine. Water is an inorganic substance. The three forms of matter can also prevail among many organic compounds.  For example, if one heats a piece of camphor gum in an evaporating dish or in a cup, he will observe the following phenomena: The solid particle of camphor turns to a clear liquid. In other words, the camphor, when first heated, passes from a solid to a liquid state by melting. On continued application heat, the camphor will finally volatilize and become invisible. On leading the vapors of camphor over a cool surface, the organic vaporous material will solidify and deposit again as solid camphor.  During all these physical changes there is no alteration in the chemical composition of the camphor. This same statement also applies to the inorganic material - water.

DIVISION OF MATTER

It is possible to divide inorganic and organic matter into very minute particles. Glass, for example, may be broken up into fine fragments, and even ground to dust. In the manufacture of Portland cement we find a typical application of the production of fine particles of inorganic matter by intensive grinding of mineral substances.  Every single particle of the dust of a pulverized substance represents the same composition as that of the original material before grinding. A wild animal running through a forest, like a fox or deer, may emit odious particles in his travels that cannot be seen by any human eye, yet the hound can easily pick the scent and follow them for miles and for hours after the fox or deer has passed a given point. The odorous principle of a fragrant flower can be detected by the sense of smell in an atmospheric dilution corresponding to a percentage of composition that is indeterminable.

GILBERT CHEMISTRY 43

EXPERIMENT 15 - Division of Matter
Take a pinch of common salt (sodium chloride) and dissolve it in water.  Now taste the solution.  You will be able to detect the characteristic taste of the salt in the solution, although you cannot see it with the human eye. Now add an equal volume of pure water to the salt solution. Mix well, and then taste the solution. You will find that you are still able to discern the taste of salt. Dilute once more with an equal volume of water and then taste again the resulting solution. Now you can imagine the thousands of particles of salt there must be in your water solution to enable you detect it by taste and yet not to see it.

EXPERIMENT 16 - Division of matter
Take a crystal of potassium permanganate and dissolve it in a tumbler of water.  Observe the coloration of the fluid. The small particles of the original crystal are now present in all parts of the water. Their color in solution allows them to be seen. The performance of this experiment allows you to visualize to what an extent matter may be divided.  Allow a part of the colored solution to evaporate to dryness and note that the dissolved permanganate  can be recovered in solid form.

EXPERIMENT 17 - Division of matter



Drop into a clear dry test tube a crystal of iodine which may be obtained in any drug store and insert a common cork lightly into the mouth of the test tube (Figure 17), Hold the test tube over an alcohol or candle lame and warm gently. Watch the beautiful purple gas that's formed and observe how it creeps, upward toward the mouth of the test tube.  Here you have another demonstration of extreme divisibility; the solid particles of iodine having been volatilized by heat and divided into thousands of small gaseous particles of iodine which are visible to the eye.

44 GILBERT CHEMISTRY

 
INORGANIC AND ORGANIC MOLECULES

Molecules are small particles of matter. The three foregoing experiments that we have asked you to perform have led chemists to the conclusion that ordinary matter is composed of particles and that these particles are so small and so minute in size that they cannot be detected with the human eye or even under the magnification of the most powerful microscope. These sub-divisions into minute particles of matter have been designated as molecular in nature. As we proceed to experimentation in chemistry, we will speak of these different particles of matter as molecules, and we shall be instructed in accordance with a law of chemistry, which may be stated as follows The smallest particle into which matter can be sub-divided without changing its chemical nature, is a molecule.  Having adopted a designation-"molecule"-to define the smallest particle of any substance which has all of the properties of the whole substance, it is now easier to explain the physical difference between solids, liquids and gases.

MOBILITY OF MOLECULES IN SOLIDS, LIQUIDS AND GASES

In a solid substance, the chemist conceives molecules as being firmly held together.  They are not free to move about to any great extent, and are assumed to have had positions. For this reason a solid substance retains its form or shape. Many substances assume definite crystalline form of great beauty. In crystals we have evidence to support the conclusion that the molecules are arranged in an orderly fashion and that it is due to this orderly arrangement of the molecules of both inorganic and organic substances that crystals assume such beautiful symmetry. We have no better illustration of variations in crystalline form than that revealed by snow flakes. In other words, the face of a crystal is composed theoretically of a layer of orderly arranged molecules or lattice structure of the particular substance under consideration. In a liquid, on the other hand, the molecules are assumed to be free to move about among themselves much more freely than is possible in a solid. For this reason liquids flow and assume the shape of the receptacle in which they are inclosed. Solids can be fractured by friction and ground into smaller sub-divisions, while a liquid will withstand great pressure and cannot be divided by a frictional force. Gas molecules are assumed to be entirely separate and mingle with each other and fly apart very widely when they are allowed to leave the space in which they are confined.  In other words, the molecules are mobile, and due to this property, we speak of a gas as being volatile and easily diffused. The molecules of a gas move about much more rapidly than those of a liquid or a solid. To illustrate, the walls of a football are kept pushed out by the constant pressure and hammering of millions of air molecules that are enclosed within the walls of the football. Also the pressure within a steam boiler is caused by the molecules of water in the form of water vapor which press constantly against the sides of the boiler.

PHYSICAL PROPERTIES OF MATTER MASS AND VOLUME

All matter occupies space. The displacement of space occupied is called volume. A bushel, a quart, a liter represent, respectively, a unit of space or a measure of volume of space occupied by a particular substance.  The space occupied by a known weight of solid, liquid, or gas varies according to the density of the material.  By specific

GILBERT CHEMISTRY 45

gravity we mean the relation between the volume and the weight of a substance. Water is used as the standard, that is, 1 cubic centimeter of water at 4 degrees Centigrade weighs 1 gram. Thus, if we have 1 cubic centimeter of a substance which weighs 5 grams it has a specific gravity of 5.

The specific gravity of a substance often enables us to tell whether or not that that substance has been adulterated.  For example, a certain oil may have a specific gravity of 2.  If the specific gravity when measured is 1.7, for example, the oil has been adulterated with some other substance.

EXPERIMENT 18 - To demonstrate the specific gravity of liquids
Place a fresh egg in a glass full of water and notice that it sinks to the bottom. Now remove the egg and dissolve two spoonfuls of salt in the water. Then put the egg into the salt solution and notice that it floats.

The reason why the egg floated in the salt solution was because we increased the specific gravity of the water beyond that of the egg.  The specific gravity of a solution is always greater than that of the pure liquid. This is the reason why it is easier to swim in salt water than in fresh water.

MALLEABILITY

By malleability is meant having the property of being rolled out or flattened without fracture.  This property is characteristic of many metals. Of all the metals, platinum and gold are the most malleable, and gold can be rolled into leaves so thin that it would take 300,000 of these leaves to make the thickness of one inch. Iron is a very malleable metal when hot, and can be moulded into many shapes and forms available for human needs. Many hundreds of men are employed daily in large steel mills in this country, rolling iron into steel rails for railroads, girders for buildings and bridges, sheets of metal for roofs, and construction of oil tanks, and many other applications made possible by the ingenuity of man.

DUCTILITY

Ductility means having the property of being drawn out into a fine thread or wire.  Iron, copper, platinum, gold, and many other metals are characterized by this property. Ductile metals find wide application in industry, especially the electrical industry. It is interesting to know that the strength of some metals is increased by drawing them out into small wires and for this reason a drawn wire is stronger than an ordinary piece of metal of the same dimensions. Large cables made by twisting iron wire together are very much stronger than solid iron rods of the same size. Cables of this type are used in the construction of suspension bridges, of which the George Washington Bridge extending over the Hudson River, near New York City, is an excellent example.

BRITTLENESS

By brittleness is meant having the property of crumbling into small particles when struck a heavy blow with a hammer.  Excellent examples of a few substances which are brittle are ordinary glass, ivory, chalk, ice, egg shells, and almost all rock.

ELASTICITY

By elasticity is meant having the property of returning to the original form when it has been changed by some force applied to a substance. By the return to the orig-

46 GILBERT CHEMISTRY

inal form, the molecules of the substance apparently tend to return to the places they formerly occupied before the change. Substances possessing this characteristic property are spoken of as being elastic substances. The one outstanding illustration of a substance having this unique property is ordinary rubber. In the stretching of a piece of rubber we disturb the arrangement of the molecules of this material.

HARDNESS

A solid is said to be harder than another solid when it will scratch or make a mark on the other substance. For example, a diamond will scratch, and even cut glass, because it is harder than glass. You can cut ordinary metallic lead with a knife blade because it is softer than the metal of the knife.

FUNDAMENTAL PHYSICAL CONSTANTS WIDELY USED BY THE CHEMIST

FREEZING POINT OR MELTING POINT

The melting point of a solid is that temperature at which it is converted to a liquid.  lt is a physical constant which is characteristic of all substances that are chemically pure. For example, ice has a melting point of 0° C., or 32° F. above which temperature it is slowly converted into water. The freezing point of water (liquid) corresponds to the melting point of ice (solid).

SUPER-COOLING

This is the property of being able to retain the liquid form when cooled below the temperature of freezing or solidification.  Liquids that assume such a physical state are very susceptible to outside forces and easily assume a solid form when agitated.

BOILING POINT

This is the temperature at which a liquid is converted into a vapor. The constant is dependent upon the atmospheric pressure existing at the time of distillation of the liquid. For example, water will boil at a lower temperature at a high altitude, as on a mountain top, than it will at sea level.  In other words, the boiling point varies according to the variations in barometric pressure.  We have many liquids that cannot be distilled at ordinary pressure without decomposition, but if such substances are distilled in a vacuum, they can be easily purified without destruction. The instrument which is used by the chemist for determining melting points and boiling points is a thermometer, and two thermometer scales find application in chemical practice - the Fahrenheit and the Centigrade scales. According to the Fahrenheit scale, water freezes at 32° above the zero point, and boils at 212°.  According to the Centigrade scale, the freezing point of water is 0°, and the boiling point is 100°. In chemical practice and also for recording scientific data in chemical publications we today make use of constants as record by both the Centigrade and Fahrenheit scales.

SUPER-HEATING

Many liquids of high boiling points are very susceptible to super-heating due to the uneven absorption of heat when the liquid is being heated to its boiling point.  This

GILBERT CHEMISTRY 47

physical phenomenon is illustrated by the result of rapid heating of water in a test tube.  If heated over a free flame without agitating the liquid the lower part of the solution will be over-heated and as a result there will be a sudden evolution of steam followed by a violent boiling of the fluid. This is referred to by the chemist as "bumping."  Unless precautions are taken during the heating of liquids, super-heating may result, leading to serious accidents.

MEASURING TEMPERATURE

There are two different scales for measuring temperature, the Fahrenheit scale and the Centigrade scale.

The Fahrenheit scale is most commonly used in our household thermometers and by the Weather Bureau, but in almost all scientific work, including chemistry, the Centigrade scale is used.  On the Centigrade scale the point at which water freezes under normal pressure is marked zero, and the point at which water boils is marked 100.

The freezing point of water = 0 degrees Centigrade or 32 degrees Fahrenheit.

The boiling point of water = 100 degrees Centigrade or 212 degrees Fahrenheit.

1 degree Fahrenheit =  five-ninths degrees Centigrade.

To convert Fahrenheit to Centigrade or the reverse use these formulas:

C degrees = (five-ninths X F degrees = 32) [NOTE: Should read: C degrees = (five-ninths X F degrees - 32)]

F degrees = (nine-fifths X C degrees + 32)

THE ELEMENTS AND CHEMICAL CHANGE

All of the changes which take place in chemical reactions are based on the actions of certain substances which the chemist calls "elements."  A boy or girl should, therefore, first acquire the correct meaning of this term if he or she is to perform understandingly chemical experiments.  By elements the chemist means those substances which he is not able to break up into simpler substances.  An element may be a solid, such as copper or iron; a liquid, such as mercury; or a gas, such as oxygen or hydrogen.  It is also important to emphasize here the fact that some elements can exist in all of the three different physical forms.  For example, ordinary iron is a solid, but will become a liquid if heated hot enough, or if heated at a very high temperature, it will become a gas.  Mercury can be heated to form a gas, or it can be cooled to form a solid.  The gas oxygen can be cooled to a liquid: or when cooled still further, to a solid.  In all of these physical changes of iron, mercury and oxygen, brought about by changes of temperature. we have not altered the elementary nature of these three substances.

More than ninety of these elements have been discovered to date, and we know that they combine in millions of different ways to form every substance that we know of on our earth.  When elements combine with each other they form what the scientist calls "compounds."  When  elements are converted into compounds, they lose their chemical identity and we create new substances possessing different properties. Such phenomena we explain as chemical changes, and the chemist speaks of such chemical changes also as chemical reactions.  For example, sulphur is an element and oxygen is an element.  When the sulphur is heated it attracts to itself the element oxygen, and undergoes a chemical change.  In other words, the sulphur and oxygen undergo a chemical reaction to form a compound which is a gas - sulphur dioxide.  This gas finds wide commercial application as a bleaching agent, and also in the manufacture of electric refrigerators.  The study of the elements and compounds, their properties, their chemical changes, and reactions is called Chemistry.

48 GILBERT CHEMISTRY

THE ATOMIC THEORY

Under the heading - Inorganic and Organic Molecules - we have a definition of the term "molecule," and stated that this is the smallest particle into which matter can be divided without changing its chemical nature. This definition of a molecule applies to both elements and compounds, and just as long as one does not subject an element or a compound to an experimental condition which leads to a chemical change or reaction, the substance is said to retain its original form.

When a chemical change or reaction takes place, the molecules of an element or compound are destroyed and new molecules are formed.  ln order to interpret such phenomena, it became necessary for the chemist to originate an imaginary concept or postulation as a working hypothesis.  The result was the creation of a general law of nature which has been for several years the fundamental basis of chemical reasoning.  This fundamental theory of chemistry is known as the Atomic Theory. The chemist's explanation of chemical change or chemical reaction on the basis of the Atomic Theory is as follows:  He assumes that there are particles in matter that are much smaller than the molecules to which we have previous! referred. This division of molecules takes place under conditions favoring a chemical change, and when molecules break up into these new imaginary particles the substance becomes very unstable and very reactive.  The chemist has named these invisible and imaginary units "atoms," and when compounds are formed by interaction of elements or otherwise, it is the atoms that involved, and new compounds are formed. In other words, molecules of elements or compounds lose their physical identity when they react chemically to form new substances, and are converted first into atoms. These atoms are very unstable and cannot exist alone, and consequently seek other atoms to make new molecules. The result, in a chemical sense, is a chemical reaction, with formation of a new substance having entirely different chemical and physical properties than those of the original substances brought together.

Therefore, as a result of the above reasoning, chemists have adopted the law of the atom to guide them in their chemical reasoning. lt is as follows: An atom is the smallest particle into which matter is divided in chemical changes.   Chemistry then has a much broader meaning when we work according to such a theory, and may be defined as the science of atoms, and how atoms combine with each other to form compounds.

The interaction of sulphur and oxygen may now be explained as follows:  When these two elements combine with each other it is not the molecule of sulphur and oxygen that react, but their atoms. The atoms on being formed cannot exist alone, and attract each other, leading to the formation of a new compound in which the properties of sulphur and oxygen have been lost entirely. An atom of sulphur (S) combines with two atoms of Oxygen (O2) to form a new substance, or gas (SO2) . The combination of two different atoms in this case leads to the formation of a new molecule.

THE MODERN CONCEPTION OF THE ATOM

Great advances in the science of chemistry and physics have been made by scientists in the last twenty-five years.  New theories regarding structure have been advanced which have led to a complete revolution of previous concepts.  According to the newer theories of the structure of matter, the atom is not the smallest particle which functions in a chemical change, but we now conceive the existence a still smaller unit than the atom, - namely, the electron. This new conception of chemical change is electrical in nature and the electron is the unit of electrical charge. These newer postulations are constantly undergoing modification and are far too advanced and theoretical to be comprehended by boys and girls for whom this manual is written, but it is not

GILBERT CHEMISTRY 49

out of place to record here some of the conclusions that have been accepted and which are influencing the development of modern chemical reasoning. The modern concepts regarding the structure of atoms may be stated briedy as follows:

1. Each of the 92 elements which we believe to constitute all matter is made up of atoms.
2. Atoms in turn consist of units which we call protons and electrons.
3. Protons are units charged positively and electrons are units charged negatively.
4. Every atom contains an equal number of positive and negative charged units.
5. The atom owes the greater part of its weight to the positively charged protons.
6. All of the protons and a part of the electrons of each atom are concentrated within a small space at the center of the atom. The remaining electrons are located in layers or "shells" outside of the nucleus. The nucleus may be conceived therefore as the sun of a planetary system around which rotate the planets (electrons).  [NOTE:  # 6 is definitely not considered correct today.  There are protons and neutrons in the nucleus and electrons in the area surrounding the nucleus.  Remember, this was 1936, and not all of what we know about the atom had been discovered by that time!]

KINDS OF CHEMICAL CHANGE

In general, there are four kinds of chemical changes which we need to consider, and every chemical reaction illustrated in this book will come under one of these changes.  We illustrate by experiments the four important types of chemical reactions of elements.  First, we have that of Direct Union, or the combining of two elements to form a compound; secondly, we have what the chemist refers to as Decomposition or Degradation, which means the breaking down of a compound into its elements or into simpler substances; thirdly, what is called Double Decomposition or the exchange of elements in two or more substances to form new compounds; and fourthly, Substitution or Replacement, a reaction in which one element takes the place of another in a compound, the substituted element being set free.

CHEMICAL CHANGE THROUGH DEGRADATION BY HEAT

EXPERIMENT 19 - Decomposition of sugar
Put two measures of granulated or table sugar in a dry test tube and cautiously heat the tube over an aalcohol lamp. Note the change in color of the sugar and its tendency to liquify.  Watch the molten sugar and continue heating until it begins to char and turn black.  Here we have a simple demonstration of degradation of an organic substance by hear.  A chemical change has taken place by heating, leading to destruction of the sugar molecules with formation of water molecules and ordinary carbon.  The identity of the carbon is disguised in the colorless sugar molecule, but is revealed when the sugar molecule undergoes decomposition.  It is a very common property of many organic substances to decompose on heating. All organic animal matter decomposes on intense heating.

DECOMPOSITION OF AN INORGANIC SALT BY HEATING

EXPERIMENT 20 - Decomposition of sodium thiosulphate
Place 3 measures of sodium thiosulphate in a clean, dry test tube and, using a test tube holder so as not to burn the fingers, heat over the alcohol lamp. You will notice that moisture forms on the inside of the test tube and some steam will be given off.  Sodium thiosulphate contains water of crystallization which is driven off in the

50 GILBERT CHEMISTRY

form of steam when the substance is heated. On further heating you will notice that sulphur is driven of and is deposited on the upper part-of the test tube. You will recognize the odor of hydrogen sulphide gas. The material left in the bottom of the tube consists of sodium sulphate and sodium sulphide. The results of heating may be represented as follows:

sodium thiosulphate + heat = water + sulphur +  hydrogen sulphide + sodium sulphate + sodium sulfide

CHEMICAL CHANGE BY DOUBLE DECOMPOSITION

EXPERIMENT 21 - Action of ferric ammonium sulphate on calcium oxide
In a test tube of cold water add 1/2 measure of ferric (iron) ammonium sulphate.  Place the thumb over the mouth of the test tube and shake to dissolve the solid. Now add 1/2 measure of powdered calcium oxide and shake again. A reddish brown precipitate is formed.

The iron of the ferric ammonium sulphate changes places with the calcium of the calcium oxide to form calcium sulphate and ferric (iron) hydroxide, which is insoluble in water, and appears as a reddish-brown precipitate.

EXPERIMENT 22 - Action of aluminum sulphate on strontium nitrate
Dissolve 1 measure of aluminum sulphate in a test tube 1/4 full of water. In another test tube 1/4 full of water dissolve 2 measures of strontium nitrate. Now pour the contents of the second tube into the first and observe the formation of a white precipitate.  The aluminum of the aluminum sulphate changed places with the strontium of the strontium nitrate to form the soluble compound aluminum nitrate, and the white precipitate of strontium sulphate which is very insoluble in water.

SUBSTITUTION OR THE DISPLACEMENT OF ONE ELEMENT BY ANOTHER

EXPERIMENT 23 - Action of iron on copper sulphate
Add 1 measure of copper sulphate to a test tube half full of water. Close the mouth of the test tube with your thumb and shake until all the solid is entirely dissolved.  This gives a blue solution of copper sulphate commonly known as blue vitriol.

Now add 1 measure of powdered iron to the copper sulphate solution and shake the contents of the test tube for a few minutes. The green color of the copper sulphate solution will gradually disappear and the iron will become covered with a red deposit of copper.

EXPERIMENT 24 - Action of zinc on copper sulphate
Repeat the preceding experiment, using powdered zinc in place of the iron.  Notice that practically the same results are obtained.

EXPERIMENT 25 - Action of magnesium on copper sulphate
Repeat the preceding experiment, using powdered magnesium in place of the iron.  Notice that in this experiment similar results are obtained.

EXPERIMENT 26 - Action of zinc on hydrochloric acid
Dissolve 3 measures of sodium bisulphate and 4 measures of ammonium chloride in a test tube 1/4 full of water. The sodium bisulphate reacts with the ammonium chloride to form hydrochloric acid which is soluble in water. Heat cautiously over an alcohol

GILBERT CHEMISTRY 51

lamp until a clear solution is obtained. Now add to this acid solution 1 measure of powdered zinc and you will observe an immediate reaction and bubbles of gas will be generated.  This gas is hydrogen formed by action of zinc on the hydrochloric acid. 

CHEMICAL CHANGE BY DIRECT UNION OF ELEMENTS

EXPERIMENT 27 - Union of zinc with sulphur
Both zinc and sulphur are elements. Mix 1 measure of powdered zinc with an equal amount of sulphur on a piece of white paper. This is not a chemical compound, for we could readily separate the sulphur from the zinc mechanically by treating the mixture with carbon bisulphide which would dissolve the sulphur and leave the zinc behind.

Place this mixture on the cover of a baking powder can and heat over the candle flame or alcohol lamp for a few minutes, keeping the face a safe distance away from the cover until the reaction is apparently over. You will note that the sulphur and zinc suddenly flash up and combine. The zinc reacts with the sulphur directly to form a compound called zinc sulphide. This substance is different from the original mixture, for if we break this up into a powder and treat it with carbon bisulphide we cannot dissolve out the sulphur, for it is now in chemical combination with the zinc.

Break up the zinc sulphide which you have just made into a powder by grinding in a mortar and put some of this into a dry test tube. Add one measure of sodium bisulphate, a few drops of water and warm over a flame for a minute. Remove the test tube from the flame and smell the gas given off.  This is hydrogen sulphide.  This is the gas formed in eggs when they decompose.

EXPERIMENT 28 - Union of magnesium with oxygen
Place a small amount, only 1/2 measure, of powdered magnesium in the spoon and and heat it over the alcohol flame, keeping your face at a safe distance. Notice the sudden flash and the light powdery substance remaining. The metal magnesium combines with oxygen in the air to form a white powdery substance called magnesium oxide.

Explanation of the behavior of the metals in the preceding experiments: The metals may be arranged in what is known as the electromotive series; that is, in the order in which they dissolve in acid solution. Metals which dissolve readily, for example, in sulphuric acid will displace those metals which do not dissolve in this acid solution or which dissolve only with difficulty. Any metal will replace any other metal below in the electromotive series, thus: -

magnesium metal + iron sulphate = magnesium sulphate + iron
zinc metal + copper sulphate = zinc sulphate + copper
tin metal + silver nitrate = tin nitrate + silver
copper metal + mercury nitrate = copper nitrate + mercury

THE ELECTRIC CELL

This is the fundamental principle of the Daniell Electric Cell. The voltage or strength of an electric cell depends upon the diference between the electrode potentials of the metals used for the two poles (+ and -) of the battery.  For example: a zinc-copper battery couple gives a greater Electro Motive Force than a zinc-lead couple or an iron-copper couple.  The farther apart the elements are in the electromotive series the greater will be the electrical voltage ofthe battery cell.

52 GILBERT CHEMISTRY

ELECTROMOTIVE SERIES

Element

Iron (ferrous)
Tin 
Lead
Iron (ferric)
Hydrogen
Copper
Silver
Mercury
Electrode potential
+0.4410
+0.1360
+0.1220
+0.0450
0.0000
-0.3400
-0.7978
-0.7986

AMERICA'S GENIUS IN THE FIELD OF ELECTRICITY

We often hear the question asked: Did the founders of science make their contributions before they were thirty or afterwards?  Practically all the pictures that are available of the different founders of science represent them as old or middle-aged men.  It is true, however, that the founders of science actually did things before they were thirty.  The things that they did were discoveries made, theories advanced, laws formulated,  classic experiments performed, and methods of teaching which commanded the attention of the public.  The important things that they did did not receive much attention at the time they did them, but since their work, they have been given credit and recognition. Thomas A. Edison began his important work when he was a very young man, and his invention of the incandescent lamp was one of his earliest contributions.  Mr. Edison was a ceaseless worker and continued to take an active interest in his work until his death. Every American boy should be proud of the record of this wonderful man.

THE ATMOSPHERE

The air enveloping our earth is essentially a mixture of two elements - oxygen, which comprises about one-fifth of the air by volume, and nitrogen, four-fifths volume. Actually, oxygen and nitrogen comprise 99 per cent of the atmosphere by volume at sea level, the remaining one per cent being made up of a mixture of gases, namely argon, helium and neon, mixed with traces of hydrogen and carbon dioxide. Oxygen is considered to be the most abundant of all the elements and most widely distributed. Eight-ninths of water by weight is combined oxygen. Such common materials as sandstone, quartz, limestone or marble, common brick, granite, clay and cement contain fully one-half their weight of oxygen.  About two-thirds of the weight of the human body is oxygen. The total weight oxygen in the land, the water,the atmosphere, and in living organisms may be regarded as very nearly equal to the combined weights of all the other elements.

OXYGEN

Oxygen of the air plays a very important role in our everyday life. We breathe this element into our lungs and from these organs it is carried by the blood-stream throughout the body to combine with the waste products of body metabolism.  These waste materials are oxidized by the oxygen, carried in the blood stream throughout the body to carbon dioxide which is carried back to the lungs by the blood and is there passed out into the air when we breathe. lt is very essential, therefore, that we breathe in fresh air if we wish to enjoy good health. Pure oxygen is a very active element, and if it were not

GILBERT CHEMISTRY 53

for the fact that the oxygen of the air is diluted with nitrogen gas, a very inactive substance, the world would soon burn up and all living organisms be destroyed.

Oxygen is said to support combustion, but the gas will not burn itself. A fire will not burn unless air rich in oxygen is constantly supplied so that the fuel can have plenty of oxygen to support comustion. Substances cannot burn without oxygen.

OXYGEN EXPERIMENTS

EXPERIMENT 29 - To remove oxygen from the air



Place a candle in the center of an ordinary wash pan by allowing a little of the melted wax of the candle to fall on the pan to stick the candle firmly. Then pour into the pan two inches of water (Figure 18). Light the candle and place over it a mason or fruit jar.  Be sure that the jar is high enough so that the flame does not come too close to the top of the jar.

You will notice that very soon the flame grows dim and finally dies out, the oxygen of the air within the jar having been entirely used up. Notice that the water begins to rise inside the jar and stands at a higher level than the Water in the pan. This is because the oxygen was removed forming a partial vacuum which drew the water up inside the jar.  The oxygen in the jar united with the carbon in the flame to form carbon dioxide, a gas which dissolves in water, and with hydrogen to form steam. which condenses in water.  The gas remaining in the jar is nitrogen.

EXPERIMENT 30 - Preparation of oxygen and how to test for it
Fill a test tube about half full of ordinary hydrogen peroxide or dioxygen solution (which may be purchased at a drug store) and add 1 or 2 measures of manganese dioxide.  Notice what takes place.



Now light a splinter of wood or string, blow out the flame, being sure that there is a spark remaining on the wood or string and lower the spark into the tube above the liquid. (Figure 19). Notice that the wood or string takes fire and burns with a flame.  This is the way to test for oxygen.

Hydrogen peroxide is a liquid composed of two atoms of hydrogen and two atoms of oxygen just as water is composed of two atoms of hydrogen and one atom of oxygen. The manganese dioxide is added to make the hydrogen peroxide give up part of its oxygen and in doing so remains unchanged itself. The hydrogen peroxide is decomposed into water and oxygen.  A substance 'ke manganese dioxide which causes a reaction to take place or speeds up a reaction and at the same time remains unchanged itself is called a "catalytic agent." We have many illustrations of catalytic agents or reaction promoters in chemistry, and many of them find wide commercial applications.

54 GILBERT CHEMISTRY

EXPERIMENT 31 - Preparation of oxygen from potassium permanganate
Place two measures of potassium permanganate in a clean, dry test tube and heat over an alcohol lamp. Test for the presence of oxygen the same way as in the preceding experiment.

many substances like potassium permanganate contain large amounts of oxygen, part or all of which is liberated on heating.

HYDROGEN PEROXIDE

Hydrogen peroxide is a chemical which every boy and girl should be familiar with.  It is found in every "First-Aid Cabinet" and is a good antiseptic. Its antiseptic properties are based on its containing an extra oxygen atom which it gives up very easily.  It is an unstable compound and sometimes the lowering of the oxygen content is due to the long time the antiseptic has been kept on the druggist’s shelf.  Sometimes, also this chemical is sold as a high grade peroxide solution when it actually never contained the required amount of excess oxygen. Hydrogen peroxide solution should never be taken by mouth.

EXPERIMENT 32-Behavior of hydrogen peroxide toward blood
Place a drop of blood on a small watch glass and then pour over the drop of blood a small quantity of hydrogen peroxide solution. Then mix the blood with the peroxide solution by stirring with a glass rod. Notice that the peroxide is decomposed with evolution of bubbles of oxygen. At the same time the red color of the blood is lost.  The blood is destroyed by the action of the generated oxygen. Many forms of bacteria are killed by contact with hydrogen peroxide.

EXPERIMENT 33-A standard test for hydrogen peroxide
Make a solution of potassium permanganate by dissolving 2 crystals of the solid salt in water as follows: Fill a test tube 1/4 full of water and add the crystals to the water. Then close the mouth of the test tube with the thumb and shake vigorously until the crystals dissolve.

In a glass one-half full of cold water put 3 drops of the potassium permanganate solution; mix thoroughly and notice the pink color of the solution. Now to this solution add 5 drops of the hydrogen peroxide solution to be tested. If the pink color is destroyed, the hydrogen peroxide solution may be considered of correct strength.  Both the potassium permanganate and hydrogen peroxide are destroyed. They cannot exist in the presence of each other.

OXIDATION

Some compounds contain much oxygen and under suitable conditions readily give up part or all of their oxygen to other compounds. Such substances are called by chemists - oxidizing agents. In other words by oxidation, is meant the union of a substance with oxygen.  During chemical oxidation heat is evolved and sometimes light.

Oxidation is an important chemical process. We obtain heat to warm our  homes in winter, and power to run machines in our factories by burning (oxidizing)  wood, oil and coal. Our houses are lighted by burning (oxidizing) gas or kerosene, or by electricity that is generated by machinery run by burning (oxidizing) fuel.  When gasoline is ignited and exploded in the cylinders of an automobile engine, the gasoline suddenly unites with the oxygen of the air which has been drawn into the cylinders.  An ordinary house heating furnace is an oxidizing machine, and even man and all living organisms (animals) are likewise active oxidizing machines. By means of heat

GILBERT CHEMISTRY 55

obtained by the process of oxidation metals can be melted. By power obtained from the process of oxidation our buildings are refrigerated and water can be frozen to artificial ice.  Ice machines are of common commercial use today, and play an important part in the preservation of health. ln fact, human life and all human activities depend upon some form of chemical oxidation and without oxygen our lives and all life activities of animals and plants would cease.

REFRIGERATION AND AIR CONDITIONING

Reversed refrigeration, or the process of heating a house in winter by means of the same equipment for cooling it in summer, is an idea which is being carefully  investigated today by engineering concerns interested in the manufacture of air-conditioning apparatus.  In summer, air-conditioning equipment absorbs heat from inside the house, takes it outside and discards it, just as an electric refrigerator takes up heatfrom inside the food compartment and releases it into the room. ln winter the cycle is reversed.  heat is taken up from out doors and brought inside to warm the house.  Coils inside the house which formerly absorbed heat, become radiators, while the outside coils, instead of throwing off heat, absorb warmth from the outside air. There are many problems yet to be solved before reversed refrigeration equipment is commercially successful, but the principle is constantly finding new applications and a promising future is ahead for new and important commercial developments.

CHEMICAL OXIDATION EXPERIMENTS

EXPERIMENT 34 - The  making of a chemical fire
There are many methods of making "chemical fire." One of these is dependent upon the fact that glycerine when in contact with solid potassium permanganate takes up oxygen from the potassium permanganate so rapidly that intense heat is created. The heat finally becomes so intense that it causes the glycerine to vaporize and the vapor finally takes fire, burning with a purple flame. The color of the flame is due to the metallic particles of potassium, resulting from the decomposition of the permanganate.

EXPERIMENT 35 - How to make a fire without a match
Upon an ordinary small tea saucer or a cover of a tin can put just three drops of glycerine - no more.  Then place on the glycerine about 5 measures of potassium permanganate crystals.  Let stand in a safe place. In a few seconds the whole mass will begin to smoke, and if the proper proportions of chemicals have been added, as indicated, the glycerine will suddenly burst into flame and burn with a blue color.

EXPERIMENT 36 - Fire ink
Place 1/2 spoonful of potassium nitrate in a test tube and add 1/2 inch of water. Warm over the candle for a minute to dissolve all the material. 

Now write with this liquid upon some unglazed or porous paper. using a clean pen or a small brush.  Be sure that the strokes are heavy and all lines are connecting. After the lines are thoroughly dry apply a lighted match or better a glowing spark to some of the writing.  Blow out any flame that may result. If properly done, the spark will travel along the lines where the liquid has been applied leaving the rest of the paper untouched.  The potassium nitrate is a strong oxidizing agent.

This experiment is very mystifying and when performed in the dark is quite phenomenal and mysterious.  The best results are obtained by using soft paper, and by making the lines heavy and connecting.

56 GILBERT CHEMISTRY

EXPERIMENT 37 - Oxidation of metallic zinc
Make a mixture of 10 measures of ammonium nitrate and 1 measure of ammonium chloride on a metal pan or plate and spread the mixture out in a thin layer.  Now sprinkle over the top of this mixture 5 measures of powdered zinc and allow 1 drop of water to fall into the mixture.

Notice that the mass soon burns, the oxidation taking place so rapidly that the zinc takes fire. The oxygen is furnished in the reaction by the ammonium nitrate, and zinc is converted into zinc oxide. Metallic iron undergoes a similar change when exposed to air and the metal burns red due to oxidation. This is spoken of in common language as “the rusting of iron."

EXPERIMENT 38 - How to make a fuse
A very good fuse can be made by soaking a cotton string in a solution of potassium nitrate or saltpetre for a few minutes and then allowing the string to dry. Allow the string to be suspended before drying. You can time your fuse by using the  proper length of string. The nitrate solution is prepared by dissolving 1/2 spoonful of potassium nitrate in a test tube containing 1/2 inch of water, and then shaking until all is dissolved.

EXPERIMENT 39 - Oxidation of an element by means of a nitrate
Heat on your spoon one measure of potassium nitrate until the salt is molten.  Then drop a pinch of sulphur into the molten potassium nitrate and notice the  sudden flash. The sulphur will be oxidized by the oxygen from the potassium nitrate to form sulphur dioxide. Note the odor of the burning sulphur. In the preceding experiment, the burning of the cotton fuse leads to the formation of carbon dioxide, an odorless gas, while sulphur burns under similar conditions to give sulphur dioxide, having a characteristic penetrating odor. '

EXPERIMENT 40 - To allow the increase in weight upon heating iron in the air
A small bundle of iron wool is counterbalanced on a beam balance. lt is then held by means of tongs, above an alcohol flame until it ignites. The iron wool is then removed from the flame until it stops sparking. The entire process is repeated until all the iron has completely burned. Upon reweighing, the increase in weight is very apparent. One must be careful not to burn the wool too rapidly so as not to lose too much of the iron in the form of sparks.

EXPERIMENT 41 - Oxidation of spices
Mix together 4 parts cinnamon, 3 parts of allspice, and 5 parts of ground cloves and grind together. Now add 8 parts of potassium nitrate to the above mixture but do not grind. Place some on a spoon and warm. Notice the odor - much like perfume.  Now ignite this mixture and you will have a phenomena as wonderful as a 4th of July night fireworks. A beautiful shower of colored fire will be the result.

EXPERIMENT 42 - Suffocating a burning candle
Attach a short piece of a candle to a cork and float this on water in a tin pan about 2 or 3 inches deep. If the candle is top heavy fasten a nail or small iron weight to the underside of the cork. Light the candle and cover it with an inverted fruit jar placed with its mouth on the base of the pan and under the water surface.  As the candle burns it becomes paler and finally the flame dies out. You will notice that the water level in the jar is higher than at the beginning of the experiment.  Some of the oxygen of the air has disappeared to support the combustion of the candle. Close the mouth of the fruit jar with a sheet of card board and set upright on the table.

GILBERT CHEMISTRY 57

EXPERIMENT 43 - Testing for carbonic acid gas
Insert a lighted taper into the jar from the preceding experiment. The flame will be extinguished.  The carbon dioxide formed by the burning candle will not support combustion.

EXPERIMENT 44 - Burning sulphur
Repeat the candle experiment using some sulphur.  Place the sulphur on a small tin lid resting on a cork.  Ignite the sulphur and burn under the fruit jar. After the flame is extinguished then set the fruit jar upright on a table and notice the color of the gas.  Also suspend a moistened blue litmus paper inside the jar. Sulphur burns to form sulphur dioxide.  Sulphur dioxide is soluble in water, forming an acid. This will turn the blue litmus paper red.

EXPERIMENT 45 - Burning iron
Collect some fragments of metallic iron and free from all iron rust in order to obtain a clean metal surface.  Tacks and small nuts and bolts are suitable. Wrap these in a piece of sheet cellophane and force firmly into the bottom of a medium sized test tube.  Then invert this tube in a pan of water, support it by a clamp and let stand for several hours.  the water will gradually rise to a higher level in the test tube, showing that air has been used up. The iron is slowly oxidized in contact with moist air and and is changed by the oxygen of the air forming iron oxide. Examine the fragments of iron and note their appearance.

EXPERIMENT 46 - Protecting iron from oxidation
Repeat the preceding experiment, but use fragments of iron which have been coated with collodion or some material impervious to moist air. The water will not rise in the jar.  You will observe that there is very little tendency here for the iron to undergo oxidation.  Paint serves to preserve iron from oxidation and corrosion.

EXPERIMENT 47 - Oxidation of zinc
Polish a strip of zinc metal and repeat the air oxidation experiment applied with iron fragments.

EXPERIMENT 48 - Oxidation in the body
The changes taking place in our body are similar to the preceding changes of the burning candle and sulphur. We are built up of complex carbon compounds, some of which contain sulphur. When we breathe we inhale air through the lungs and here the oxygen of the air is picked up by the blood and carried where needed in the body.  A burning process actually takes place internally, and the products of combustion are expelled through the lungs.  Bubble the breath through a glass tube into a test tube of lime water.  What happens?  A white precipitate of calcium carbonate is formed, showing the presence of carbon dioxide.

EXPERIMENT 49 - Combustion of charcoal
Heat 3  measures of potassium nitrate in a dry test tube over your alcohol lamp until the salt crystals liquify. Holding tube vertically then drop.into the molten salt some specks of charcoal. They will take fire immediately. The nitrate furnished oxygen to burn carbon.

EXPERIMENT  50 - Burning sulphur
Repeat the preceding experiment with sulphur.  This will burn in the presence of potassium nitrate, forming sulphur dioxide, which will be detected by its characteristic odor.

58 GILBERT CHEMISTRY

EXPERIMENT 51-Burning paper
Repeat the above experiment with fragments of dry filter paper fiber.

EXPERIMENT 52-Oxidizing copper
Insert into some molten potassium nitrate a piece of copper wire. Note the change on continued heating over your alcohol lamp.

EXPERIMENT 53-Oxidizing iron
Repeat the above experiment using a piece of iron wire.

EXPERIMENT 54-Oxidizing aluminum
Repeat the above experiment using a small piece of aluminum foil or wire.

EXPERIMENT 55-Oaidizing nickel
Repeat the above experiment using a piece of nickel wire.

EXPERIMENT 56-Oxidizing zinc
Repeat the above experiment using some granules of granulated zinc metal.

EXPERIMENT 57-Oxidizing silver
Repeat the above experiment using a piece of polished silver metal.

EXPERIMENT 58-Asbestos insulation
Repeat the preceding molten potassium nitrate experiment with some asbestos fibers.
 
EXPERIMENT 59-Cotton fiber
Repeat the above experiment with cotton fiber.  Which is the best fire insulating material, asbestos or cotton?

EXPERIMENT 60-Oxidizing sulphur in copper sulphate
Repeat the preceding experiment by fusing potassium nitrate and then dropping into the hot fluid crystals of copper sulphate. Observe the behavior and note whether you actually have an oxidation with formation of sulphur dioxide.

PROTECTION AGAINST FIRE

Intensive oxidation of combustible material leads to generation of heat and, as a final! result, to a conflagration. Cloth, wood, paper and other substances may be rendered fireproof by treating them with the proper chemicals. Ammonium chloride or sal ammoniac (NH4Cl) is a cheap salt which can he used for this purpose.  The article to be fireproofed is dipped into or soaked in a strong aqueous solution of ammonium chloride and then dried. When such treated material is heated. the ammonium chloride is decomposed with liberation of ammonia and hydrochloric acid, and a fire is prevented, as neither the ammonia or hydrochloric acid will support combustion. When they are generated they smother the flame and conflagration is prevented.  The curtain and scenery of theaters and tapestries in public buildings are fireproofed as a protection against fires. Fireproofed wood finds important commercial use as a construction material. Such chemically treated materials cannot be set on fire by sparks or flames.  Tin salts find commercial application in fireproofing.

GILBERT CHEMISTRY 59

EXPERIMENT 61 - To fireproof cloth or paper
Take a strip of paper or linen and immerse it in a solution made by dissolving one teaspoonful of ammonium chloride in a test tube 1/3 full of water. When the paper or linen is dry, try to light it with a match. You will see that it burns while held in the flame but will go out just as soon as the flame is removed.

EXPERIMENT 62 - To fireproof wood
Wood is also treated sometimes with a strong ammonium chloride solution.  Another way to fireproof wood is to paint it with water glass solution.

Holding a match by the head, dip the other end in a sodium silicate solution (water glass).  Allow the coating to dry for twenty minutes, then light the match. The flames will go out just as soon as it reaches the portion that has been dipped in the water glass solution.

EXPERIMENT 63 - Fire-proofing cloth
Cloth or other inflammable substances may be fireproofed by treating them with chemicals which when heated give off vapors that smother the flame.

Dissolve 12 measures of ammonium chloride in a test tube 1/3 full of water. Put a piece of cotton cloth 2 or 3 inches square in the bottom of a glass and pour the liquid in the test tube over it. Stir the cloth around until it is wet through, then let it dry and try to light it with a match. You will find that it will burn while held in the flame, but just as soon as the match flame is removed it will go out.

EXPERIMENT 64 - Fireproofing with sodium tungstate
Cloth, paper, wood and similar inflammable substances may be fireproofed by treating them with sodium tungstate. This process is frequently used in connection with the curtains and scenery for theaters. The woodwork on battleships is also treated in this manner so that it will not take fire from the explosion of shells.

EXPERIMENT 65 - Fireproofing with sodium silicate
A sodium silicate solution or water glass is often used for fireproofing. Wood is frequently fireproofed by means of sodium silicate. This liquid if applied to paper or cloth will cause it to become stiff when it dries, so it is not suitable for these materials.

Hold a match by the head and dip the other end into a solution of water glass (sodium silicate solution). Let the coating which is obtained dry about 15 minutes then light the match. There will be no danger of burning your lingers, for the flame will go out as soon as it reaches the water glass.

FIRE EXTINGUISHERS

Since carbon dioxide does not burn nor support combustion, it is used in fire extinguishers. You are all familiar with the hand fire extinguisher. Remember the instructions: "To operate, turn upside down." This apparatus is really no more nor less than a huge siphon, the kind you get carbonated or seltzer water from.

In the large vessel is a dilute solution of sodium carbonate. In the bottle is strong sulphuric acid. The cork is made of lead and fixed so that when the tank is turned upside down it falls from the bottle just enough to allow the sulphuric acid to trickle through slowly. (Figure 20). (A) shows an interior view of the fire extinguisher: (B) shows what happens when the extinguisher is turned upside down.

The acid liberates carbon dioxide from the sodium carbonate just as you liberated carbon dioxide from sodium carbonate with tartaric acid. The free gas creates a high pressure in the tank, causing large quantities of gas to dissolve in the water and forcing

60 GILBERT CHEMISTRY

out a stream of gas and water. Carbon dioxide is heavy and surrounds the flame with a blanket of unburnable gas, which prevents access of oxygen and in that way smothers the flame.

Quite recently a new style tire extinguisher has come into use. The container is built like a hand pump. ln the pumplike arrangement is a liquid called carbon tetrachloride.  This is a rather marvelous liquid. lt voliatilizes, that is, it is converted into a gas as quickly as alcohol or gasoline but it does not burn. You are familiar with the explosive power of gasoline. Here is a vapor which defies all attempts to burn it.




When directed at the base of the flame the spray of carbon tetrachloride quickly forms a gas which surrounds the burning oil or wood or whatever it is like a blanket and prevents the access of oxygen. Without oxygen there can be no combustion, so the fire is smothered. 

Carbon tetrachloride is also a splendid solvent. It is used to remove grease and paint spots from clothing and to clean white leather. You have probably noticed advertisements of spot removers which do not burn. All of these contain carbon tetrachloride.

EXPERIMENT 66 - Carbon tetrachloride, a fire extinguisher
Pour a little carbon tetrachloride on a piece of paper and light the paper with a match. Notice that the paper will not burn, proving that carbon tetrachloride does not support combustion and will not burn. This is an example of a wet fire extinguisher.

EXPERIMENT 67 - A hand grenade fire extinguisher
Take 2 test tubes of crude calcium chloride; 2 spoonfuls of common salt and 1 cup of water and place in thin bottles. In case of fire, a bottle of this mixture thrown so that it will break near the flames will put the fire out. This mixture is better and cheaper than most of the grenades sold for the purpose of fire protection.


Go to Gilbert Chemistry - Part 4    or   Back to the A.C. Gilbert Collection

"The Science Notebook"  Copyright 2008-2017 - Norman Young