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  Lionel Chem-Lab - Chapter 6

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NOTE:  This book was published in 1942 as a manual to accompany several Lionel 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  In addition, much of the information contained in this book about chemistry and other subjects is outdated and some of it is inaccurate.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 102 - 111

CHAPTER VI

THE HALOGENS

The halogens, a term meaning "producers of salt", includes a family of four elements, which, listed according to their degree of activity, are: fluorine, chlorine, bromine and iodine. It is natural that the chemist should group these four elements together because each possesses certain properties common to the others. When combined with metals they form compounds strikingly similar to common salt, hence the name "salt producers".

These elements are of the utmost commercial importance. Chlorine undoubtedly is the most essential of the four due to its industrial use in munitions, bleaching and disinfecting. Sodium chloride and hydrochloric acid are two very important compounds of chlorine which have many wide uses not only in medicine but in the chemical industries.

The other three elements and their compounds enjoy a multitude of applications in the field of drugs, dyes, medicines, antiseptics, bleaching agents and photographic chemicals.

FLUORINE

Fluorine is one element which few people have ever seen because of its rarity and the great difficulty required to prepare it. Since it is very active, its compounds occur abundantly in the earth as calcium fluoride (fluorspar) and cryolite. In its free state, poisonous fluorine is a pale yellow gas somewhat heavier than air with a pungent odor.

Hydrogen fluoride, one of the important compounds of fluorine, is a liquid prepared by the action of sulfuric acid on fluorspar. When this liquid is dissolved in water, hydrofluoric acid is formed. One of the peculiarities of this acid is that it is very corrosive and attacks glass. For this reason, chemists have to keep it in wax bottles, and handle it with the utmost caution. However, the fact that it does attack glass makes it most useful in etching and frosting processes. Frosted light bulbs, for example, are etched on the inside by the action of hydrofluoric acid.

EXPERIMENT No. 131 A Test For Calcium Fluoride

(CL-66, CL-77)

APPARATUS: Calcium fluoride, heating spoon and alcohol lamp.

102


LIONEL CHEM-LAB 103

PROCEDURE: Place one measure of calcium fluoride in the heating spoon and heat it, using a blowpipe if necessary. Continue heating until the substance fuses or melts. Moisten a piece of litmus paper and place it on the melted substance.

SUMMARY: When calcium fluoride is heated, it either melts or fuses and causes red litmus paper to turn blue.

EXPERIMENT No. 182 Testing For Florine

(CL-66, CL-77)

APPARATUS: Calcium fluoride, glass tubing, sodium bisulfate and alcohol lamp.

PROCEDURE: Mix one measure of calcium fluoride and one measure of sodium bisulfate on a clean sheet of paper. Place one end of a section of glass tubing in the flame of the alcohol lamp. Rotate the tubing between your fingers and heat until the end closes. Allow the tubing to cool. Put some of the mixture into the tube and follow the same procedure to close the other end of the tube. Heat the mixture and note the white smoke formed inside the closed tube.

CAUTION: Care should be taken not to smell too much of this gas since it attacks the membranes of the nose, throat and lungs.

SUMMARY: Sulfuric acid formed by heating the sodium bisulfate, reacts with calcium Huoride to form hydrofluoric acid. The fumes will etch glass.

EXPERIMENT No. 183 Decomposition Of Calcium Floride

(CL-66, CL-77)

APPARATUS: Calcium fluoride, glass tubing, sodium bisulfate, alcohol lamp.

PROCEDURE: Repeat Experiment No. 182 and pay particular attention to the white residue which forms on the walls of the glass tube.

SUMMARY: Sulfuric acid reacts with calcium fluoride to form hydrofluoric acid (the smoke) and a silicate (the residue).

CHLORINE

Scheele, a Swedish druggist, is generally credited with having discovered the important element of chlorine, a gas so-named because of its greenish-yellow color. It does not occur free in nature but in combination with numerous minerals. Although existing in many harmless compounds, free chlorine is very dangerous. During the First World War, it was commonly used as poison gas and for this reason, in performing the following experiments, we must be very careful not to smell too closely any of the fumes from the test tube even though only slight traces of the gas will be prepared.

Chlorine compounds are all about us, the one familiar to every boy and


104 THE HALOGENS

perhaps the most indispensable of all is sodium chloride, or common table salt. Other important chlorides (where chlorine is combined with a metal) are potassium chloride and magnesium chloride.

HOW CHLORINE IS MANUFACTURED

Inasmuch as no free chlorine is found in nature, it has to be obtained from its compounds. Commercially, this is done by the electrolysis of salt water. Electricity conducted through salt water results in the formation of chlorine gas. This same reaction, as you may know, has caused the death by chlorine asphyxiation of scores of men on wrecked submarines when salt water has reached the electric batteries used to propel the submarine under water.

The electrolytic method is as follows: Solid sodium or potassium chloride is first dissolved in water to make a brine. This is purified and then subjected to the influence of direct electric current in electrolytic cells. The products thus obtained are chlorine gas, sodium or potassium hydroxide solution, and hydrogen gas. The chlorine gas is purified, compressed, and cooled to a yellow liquid which is loaded into clean containers ready for shipment.

One of the largest chlorine plants is located at Niagara Falls where an abundance of electric power makes the electrolytic method of producing chlorine economical. Sodium hydroxide and hydrogen are valuable byproducts. In the laboratory, chlorine is usually prepared by oxidizing hydrochloric acid with manganese dioxide.

EXPERIMENT No. 184 Preparation Of Chlorine

(CL-66, CL-77)

APPARATUS: Manganese dioxide, hydrochloric acid, filter paper, starch test solution, two test tubes, delivery tube and stopper, candle or alcohol lamp.

PROCEDURE: Place one measure of manganese dioxide and ten drops of hydrochloric acid in a test tube. Insert the delivery tube and stopper into the mouth of the test tube. Heat the solution to the boiling point, remove from flame and collect the gas in the other test tube. Prepare some starch test solution as described in Experiment No. 688. Pour a little of this solution on a piece of filter paper. Hold a piece of this test paper over the mouth of the tube containing the gas and note the resulting color.

SUMMARY: Manganese dioxide reacts with hydrochloric acid to form manganese chloride, water and chlorine gas, When starch test paper is exposed to this gas it acquires a bluish color.

CAUTION: The residue in the first test tube should be destroyed or the chlorine gas will continue to be generated. Care should be taken

LIONEL CHEM-LAB 105

not to smell too much of the gas since it attacks the membranes of the nose, throat and lungs.

EXPERIMENT No. 185 How To Prepare Chlorine

(CL-55, CL-66, CL-77)

APPARATUS: Calcium hypochlorite, tartaric acid and test tube.

PROCEDURE: Put two measures of calcium hypochlorite in a test tube half full of water and shake to dissolve. Add one measure of tartaric acid and observe the resulting gas bubbles. Carefully note the odor coming from the mouth of the tube.

CAUTION: Care should he taken not to smell too much of this gas since it irritates the membranes of the nose, throat and lungs.

SUMMARY: In this reaction, the chlorine of the calcium hypochlorite is liberated as a gas. It is easily detectable because of its penetrating odor.

EXPERIMENT No. 186 Detecting Chlorine

(CL-55, CL-66, CL-77)

APPARATUS: Starch, sodium iodide solution, white paper, calcium hypochlorite, tartaric acid, two test tubes, alcohol lamp or candle.

PROCEDURE: Place in a test tube one measure of starch, a few drops of water, and three drops of sodium iodide solution. Add one half a test tube of boiling hot water. Heat this solution until it boils. Allow to cool. Put two measures of calcium hypochlorite in a second test tube half full of water and shake vigorously. Add two measures of tartaric acid to the calcium hypochlorite solution. Heat gently and note the odor of chlorine gas. Dip the white paper into the starch solution and place the wet paper over the mouth of the test tube containing the gas.

SUMMARY: When the chlorine gas comes in contact with the starch test paper, it reacts with the sodium iodide to form sodium chloride and liberates free iodine which turns blue in the presence of starch.

EXPERIMENT No. 187 Protection Against Chlorine

{CL-55, CL-66, CL-77)

APPARATUS: Sodium thiosulfate, sodium carbonate, cotton, calcium hypochlorite, tartaric acid and two test tubes.

PROCEDURE: Pour three measures of sodium thiosulfate and three measures of sodium carbonate in a test tube half full of water. Shake to dissolve. Soak a wad of cotton in this solution for two or three minutes. Allow to dry. Dissolve one measure of calcium hypochlorite in another test tube half full of water. Close the mouth of the test tube with your thumb and shake vigorously. Add one measure of tartaric acid. Place the wad of cotton over the mouth of the second test tube which is generating chlorine gas. Smell cotton and note the absence of any odor.


106 A THE HALOGENS

SUMMARY: The sodium thiosulfate converts the chlorine into a harmless substance and renders it odorless.

EXPERIMENT No. 188 Testing For Chlorine In Organic Compounds

(CL-66, CL-77)

APPARATUS: Thin copper wire, carbon tetrachloride, alcohol lamp.

PROCEDURE: Bend one end of the copper wire into a loop about one eighth of an inch in diameter. Hold loop over flame until the flame loses its bright color. Allow to cool. Dip wire into carbon tetrachloride bottle and reheat it immediately. Note the green colored flame.

SUMMARY: Organic compounds containing chlorine give a green color to the flame.

EXPERIMENT No. 189 How Chlorine Reacts To Copper

(CL-55, CL-66, CL-77)

APPARATUS: Calcium hypochlorite, tartaric acid, piece of copper, test tube, delivery tube and stopper, candle or alcohol lamp.

PROCEDURE: Place two measures of calcium hypochlorite in a test tube filled with water. Shake vigorously. Add two measures of tartaric acid. Attach delivery tube and stopper. Heat gently. Place a piece of copper in the stem of the delivery tube. Note the tarnishing of the metal.

SUMMARY: The tarnishing of the copper is due to the chlorine. Chlorine is very active and all the familiar metals, with the possible exception of gold and platinum, react readily with it.

EXPERIMENT No. 190 Chlorine And Sodium Thiosulfate

(CL-55, CL-66, CL-77)

APPARATUS: Sodium thiosulfate, calcium hypochlorite, tartaric acid, gas delivery tube and stopper, two test tubes.

PROCEDURE: Place three measures of sodium thiosulfate in a test tube half full of water and shake to dissolve. Dissolve two measures of calcium hypochlorite in another test tube half full of water. Add two measures of tartaric acid to the calcium hypochlorite solution. Quickly attach gas delivery tube and stopper to the tube of calcium hypochlorite solution with the long stem running into the sodium thiosulfate test tube. Note the white precipitate when the chlorine gas passes into the test tube of sodium thiosulfate.

SUMMARY: This reaction causes sodium thiosulfate to decompose and form sulfur, which settles as a white precipitate. The chlorine reacts with the sodium to form sodium chloride. Thus, the chlorine is converted into a harmless substance by the sodium thiosulfate.

Of the many uses of chlorine, the two principal ones are in bleaching and purification of drinking water.


LIONEL CHEM-LAB 107

Chlorine forms bleach liquor when absorbed in water or in lime or alkali solutions, and such solutions are widely used as bleaching agents in the textile, pulp and paper, shellac and other manufacturing industries as well as in households and laundries. Calcium hypochlorite is an example of a chlorine compound used for bleaching.

The pulp and paper industry is the largest industrial consumer of chlorine, while the second most important application is in the manufacture of organic chemicals.

EXPERIMENT No. 191 How Chlorine Bleaches Cloth And Paper

(CL-55, CL-66, CL-77)

APPARATUS: Calcium hypochlorite, bits of colored paper, some small pieces of dyed cotton cloth, acetic acid, saucer and glass.

PROCEDURE: Place five measures of calcium hypochlorite in a glass containing about an inch of water. Stir solution thoroughly. Drop in the paper and cloth. Add three drops of acetic acid and cover glass with a saucer. Set the glass aside for a few hours. Take out the materials, rinse with water and allow to dry. Note how the colors have been bleached.

SUMMARY: Calcium hypochlorite, or bleaching powder, as it is commonly called, is an unstable compound giving off chlorine in the presence of an acid. This chlorine gas sets the oxygen free from the water and the oxygen so liberated combines with the dye substance in the cloth or paper converting it into a colorless compound. Care should be taken not to expose the materials to chlorine for too long a time or the gas will injure the fabrics.

The use of chlorine for the sterilization of water and sewage is increasing markedly, an application of utmost importance to National Health. Practically every city must purify its water supply and chlorine is used for this purpose. The terrible disease of typhoid has been practically eliminated from our American cities because our drinking water is now chlorinated. Useful chlorine compounds are chloroform and carbon tetrachloride.

EXPERIMENT No. 192 Carbon Tetrachloride

(CL-66, CL-77)

APPARATUS: Carbon tetrachloride, test tube, heating spoon and candle.

PROCEDURE: Place one drop of carbon tetrachloride in a test tube half full of water. Note where the drop settles. Shake the tube well. Note whether the carbon tetrachloride dissolves. Place a drop on your hand and blow on it. Note the cooling effect. Place several drops in the heating spoon and attempt to ignite the liquid. Note that the liquid does not burn.

SUMMARY: Carbon tetrachloride is one of the many organic compounds containing chlorine. It is heavier than water and will not

108 THE HALOGENS

mix with it. The cooling effect is due to rapid evaporation. Because it is non-inflammable and can remove grease spots from fabrics, carbon tetrachloride is used extensively as a cleaning agent in the home. (Gasoline is considered very dangerous as a spot-remover and should never be used.)

HYDROCHLORIC ACID

Chlorine has a special affinity for hydrogen. The two gases may be mixed in the dark without danger but an electric spark or bright sunlight will cause an immediate explosion since the two combine violently to form hydrogen chloride, a very important compound which forms hydrochloric acid when dissolved in water.

Commercially, hydrochloric acid is manufactured by heating sodium chloride and sulfuric acid and dissolving the resulting gas in water.

EXPERIMENT No. 193 How To Prepare Hydrochloric Acid

(CL-11, CL-22, CL-33, CL-44, CL-55, CL-66, CL-77)

APPARATUS: Sodium bisulfate, ammonium chloride (or sodium chloride), test tube, glass rod, household ammonia, candle or alcohol lamp, and blue litmus paper.

PROCEDURE: Put three measures of sodium bisulfate into a dry test tube. Add two measures of ammonium chloride or sodium chloride. Heat cautiously over a flame keeping your face away from the reaction. Note the rising of fumes. Place a strip of moistened blue litmus paper over the mouth of the test tube and note the reaction. Remove tube from flame and cautiously inhale the odor at mouth of tube. Insert glass rod into some household ammonia. Hold the rod near the mouth of the test tube. Note the appearance of white fumes.

SUMMARY: When heat was applied, hydrogen chloride gas was liberated changing the dampened blue litmus paper red. This gas is readily soluble in water and in such a solution is called hydrochloric acid.

EXPERIMENT No. 194 Properties Of Hydrochloric Acid

(CL-44, CL-55, CL-66, CL-77)

APPARATUS: Blue litmus paper, hydrochloric acid, test tube, candle or alcohol lamp.

PROCEDURE: Place a drop of hydrochloric acid on a strip of blue litmus paper. Note that the litmus paper turns red. Place two drops of hydrochloric acid in a test tube. Hold the test tube in the upper portion of flame and heat. Remove test tube from flame. Note the sharp odor. Place moistened strip of blue litmus paper at mouth of tube. Note the red color change.

SUMMARY: The changing of blue litmus paper to red is proof that the liquid is an acid. When heated, the hydrogen chloride fumes

LIONEL CHEM-LAB 109


escape (detectable because of their sharp odor). This too is acid in reaction as it changes moistened blue litmus paper red.

SODIUM CHLORIDE OR SALT

Probably no other substance except water is more used by civilized people than salt. It occurs in nature in three different forms, first in sea water, second in salt springs and third as rock salt.

The oldest method of making salt is to evaporate salt water, and this method, although crude, is still used today in many parts of the world.

The customary method of obtaining salt is by means of wells drilled into the deposits. Two pipes, one inside the other, are used and water forced down between the pipes brings salt brine to the surface via the inside pipe.

BROMINE

Bromine is a thick, light-colored liquid with an extremely disagreeable odor. It is similar to chlorine and fluorine in that it is very poisonous in both its liquid and gaseous state. Small amounts of bromine are found in salt water and can be obtained by evaporating the water. Bromine compounds are known as bromides. The principal uses of bromine are in medicine and photography, but in recent years it has achieved considerable popular recognition because of its use in tear gas.

IODINE

Iodine, the fourth and last member of the Halogen family, is by no means the least important. Originally discovered over a hundred years ago by a French chemist, to the average boy it is probably best known because of tincture of iodine, the dark-brown antiseptic which smarts when applied to a cut or wound.

EXPERIMENT No. 195 How To Prepare Iodine

(CL-55, CL-66, CL-77)

APPARATUS: Sodium iodide solution, sodium bisulfate, calcium hypochlorite and test tube.

PROCEDURE: Place two drops of sodium iodide solution in a test tube half filled with water. Add a quarter-measure of calcium hypochlorite and a measure of sodium bisulfate. Shake tube vigorously for a few seconds. Note the brownish-yellow color.

SUMMARY: When calcium hypochlorite is mixed with water in the presence of an acid, chlorine is liberated. This gas, being more active than iodine, displaces it readily from the sodium iodide solution. The free iodine turns the solution brownish-yellow.

110 THE HALOGENS

EXPERIMENT No. 196 Starch Test Detects Iodine

(CL-55, CL-66, CL-77)

APPARATUS: Three test tubes, white paper, starch, sodium iodide solution, sodium bisulfate, calcium hypochlorite, eye dropper, candle or alcohol lamp.

PROCEDURE: Add half a test tube of water to a test tube containing one measure of starch and a few drops of water. Boil for a few seconds and immerse the piece of white paper in the solution. Take paper out and dry. Place two drops of sodium iodide solution in a test tube half full of water. Add one measure of sodium bisulfate and a pinch of bleaching powder. Shake well and then place the dried starch paper into this iodine solution.

SUMMARY: A starch test solution under proper conditions will show a very definite blue color in the presence of iodine.

EXPERIMENT No. 197 Iodine Soluble In Carbon Tetrachloride

(CL-66, CL-77)

APPARATUS: Carbon tetrachloride, sodium iodide solution, sodium bisulfate, calcium hypochlorite and test tube.

PROCEDURE: Prepare iodine by placing one drop of sodium iodide solution in a test tube half full of water. Add a quarter measure of calcium hypochlorite and one measure of sodium bisulfate. Shake tube a few seconds. Add several drops of carbon tetrachloride. Shake tube vigorously. Hold tube still and allow carbon tetrachloride to mass at the bottom. Note the violet color.

SUMMARY: Iodine is more soluble in carbon tetrachloride than in water. Carbon tetrachloride being heavier than water settles at the bottom of the tube, carrying with it most of the iodine. This accounts for the violet color at the bottom of the test tube.

EXPERIMENT No. 198 Iodine Reacts With Sodium Thiosulfate

(CL-55, CL-66, CL-77)

APPARATUS: Sodium thiosulfate, sodium iodide solution, sodium bisulfate, calcium hypochlorite and two test tubes.

PROCEDURE: Pour two drops of the sodium iodide solution into a test tube half full of water. Add one measure of sodium bisulfate and a pinch of calcium hypochlorite and shake well. Note the reddish brown color. Now put two measures of sodium thiosulfate into this iodine solution and note that the color disappears.

SUMMARY: Sodium thiosulfate reacts with iodine converting it into two colorless compounds.

EXPERIMENT No. 199 Iodine Stain Remover

(CL-33, CL-44, CL-55, CL-66, CL-77)

APPARATUS: Sodium thiosulfate, test tube and iodine stain.

LIONEL CHEM-LAB 111

PROCEDURE: Dissolve five measures of sodium thiosulfate in a test tube half full of water. Apply to the iodine stain and note that the stain disappears in a short time.

SUMMARY: This is added proof that sodium thiosulfate converts iodine into colorless compounds.

EXPERIMENT No. 200 Iodized Salt Contains Iodine

(CL-55, CL-66, CL-77)

APPARATUS: Sodium bisulfate, glass, stirring rod, iodized salt, test tube, starch and calcium hypochlorite.

PROCEDURE: Dissolve by stirring, three measures of sodium bisulfate and two teaspoonfuls of iodized salt in a glass half full of water. Add one measure of calcium hypochlorite and stir. Prepare some starch solution by adding a test tube half full of boiling water to a test tube containing one measure of starch and a few drops of water. Boil for a few seconds. Pour a few drops of the cooled starch solution into the above solution and note the blue color. The blue color is proof that the salt contains iodine.
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