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COMPOSITION OF CARBON COMPOUNDS. 109

EXPERIMENT LXXVIII.

COMPOSITION OF CARBON COMPOUNDS.

Apparatus. Iron dish (sand bath), test tubes, stopper and delivery tube, ignition tube, rubber connector.

Materials. - Sugar, starch, oxalic acid, benzoic acid, powdered cupric oxide, lime-water, gelatine (powdered), soda-lime, urea, litmus.

a. In an iron dish (sand bath) heat one cubic centimeter of sugar as long as a change occurs. Repeat with starch; with a crystal of oxalic acid. Results? What proof have you that the sugar and starch contain carbon? The oxalic acid?

b. Heat half a c.c. of oxalic acid crystals in a test tube. Determine whether carbon dioxide is evolved or not. Results? Heat half a c.c. of benzoic acid in a test tube. Result? Is there any evidence of carbon dioxide?

Recall Experiment XLVIII, a. Repeat it, using one-fourth of a c.c. of benzoic acid and five times its volume of powdered cupric oxide instead of the charcoal and lead oxide. Results? Is there any evidence that hydrogen was present in the benzoic acid? What precaution is necessary to be certain, if it is known that the cupric oxide used is slightly hygroscopic?

c. Recall Experiment XXXIII, a. Repeat it, using powdered gelatine in place of the glue, and powdered soda-lime instead of slaked lime. Results? Repeat it again with urea in place of the gelatine. Conclusions? If glue and gelatine represent the class of albumins, what element must the members of this class contain?

EXPERIMENT LXXIX.

HYDROCARBONS.

Apparatus. Mortar and pestle, ignition tube 15 cm. long, ring stand, clamp, delivery tube, rubber connector, test tubes, 100 c.c. flask, wire gauze, one-hole stopper, pneumatic trough, evaporating dish.

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Materials. Dry soda-lime and fused sodium acetate, limewater, bromine water, concentrated sulphuric acid, "95 per cent" ethyl alcohol, calcium carbide, benzene.

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a. Methane. In a mortar powder and mix 2 grams of soda-lime and 1 gram of dry, fused sodium acetate. With the mixture half fill an ignition tube 15 cm. long, and attach a delivery tube by means of a rubber connector. Support the tube horizontally, tap it to insure a passage for gas, and heat it with a moving flame. Collect the evolved gas — it is impure methane (cf. § 292)

in three test tubes. Note its physical properties and combustibility. After burning a test tube of the gas, pour lime-water into the tube, close it with the thumb, and shake it. Result? Conclusion? To one test tube of methane add a drop of bromine water. Close the tube, and shake it. Does the color of the bromine disappear?

b. Ethylene. In a 100 c.c. flask cautiously add 10 c.c. of concentrated sulphuric acid to 5 c.c. of alcohol. Shake the flask after each addition of acid so as to insure mixing. Support the flask over wire gauze but not quite touching it, and attach a stopper and a delivery tube with a rubber connector. Do not leave the delivery tube in the

ETHYL ALCOHOL.

111

water when you stop heating! Heat with a small flame until a regular stream of gas comes off, and collect three test tubes full over water. Note its physical properties and the character of its flame. Test with lime-water and bromine water as in a. Results?

In a test tube mix 2 c.c.

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c. Acetylene. of water with 5 c.c. of alcohol. Add two pieces of calcium carbide the size of peas, and at once attach a stopper and delivery tube. Collect the evolved gas (acetylene) over water in three test tubes. Note its properties as

directed in a and b.

Do not inhale it.

d. Benzene. - Put half a cubic

centimeter no

more of benzene, CHÊ, in an evaporating dish. Note its odor. Carefully ignite the benzene. Describe its flame. Write the equation for the combustion of benzene, if the products are carbon dioxide and water.

EXPERIMENT LXXX.

ETHYL ALCOHOL.

Apparatus. Flask (100 c.c.), stopper and delivery tube, test tubes, evaporating dish, distilling apparatus.

Materials. Molasses (or powdered grape sugar), yeast, lime-water (or baryta water), litmus, sodium bicarbonate, alcohol, powdered shellac or rosin.

a. To 25 c.c. water in a 100 c.c. flask add 5 c.c. molasses or powdered grape sugar and about one cubic centimeter of compressed yeast. Attach tightly a stopper with a delivery tube, and let the tube pass into 5 c.c. lime-water or baryta water in a test tube. Let the

flask stand in a warm place, and note results. If you leave the delivery tube in the lime-water over night, see that it dips only slightly below the upper surface of the liquid. Why? If the test tube contains no precipitate the next day, heat its contents to boiling. Explain the result. Test the reaction of the solution in the flask toward litmus. Result?

b. Ask the teacher to collect from several students the dilute alcohol they have prepared, and to distill it, if this was not done in connection with § 280. If the first portions of the distillate do not burn when a flame is applied they must be redistilled. The first few drops may then be tested for alcohol.

c. Set some of the fermented solution aside, without stoppering the flask, for a week or two. Then note the taste of the solution, its reaction to litmus and its effect upon a little solid sodium bicarbonate in a test tube. Results?

d. Put two or three drops of alcohol into an evaporating dish, warm the dish slightly, and apply a flame. Note the color of the alcohol flame. Write the equation for its combustion.

e. Treat half a cubic centimeter of powdered shellac or rosin in a test tube, with 5 c.c. alcohol. Close the tube with the thumb, and shake it. Result? Add 5 c.c. water. Result? Let the tube stand until the next period. Result?

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Caution. -Do not bring the bottle of ether near a flame!

a. Put two drops of ether into an evaporating dish, remove the ether bottle, and apply a flame to the ether in the evaporating dish. Describe the flame.

b. In a test tube add 2 c.c. ether to a piece of paraffin half the size of a pea, shaking. Result? Pour the ether out into the evaporating dish, and hold the dish in the hand to drive off the ether. Result? Note the volatility and odor of the ether.

EXPERIMENT LXXXII.

ALDEHYDES.

Apparatus. Test tubes, stirring rod, ring stand or rack,

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Materials. Granular potassium dichromate, concentrated sulphuric acid, methyl alcohol, ethyl alcohol; solutions of silver nitrate, caustic soda, and ammonia; copper wire for spiral.

a. In a test tube add 2 c.c. of concentrated sulphuric acid to 6 c.c. of water, cool the mixture under the tap, and add 2 c.c. of alcohol. c.c. of granular potassium

Pour this mixture upon 2 dichromate in a test tube.

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