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EXPERIMENT XXXVIII.

NITROUS OXIDE.

Apparatus. Test tubes, stopper, delivery tube, pneumatic trough, clamp, ring stand, collecting bottle.

Materials.

Ammonium nitrate, pine splinter.

a. Into a test tube provided with stopper and delivery tube put about 10 grams ammonium nitrate, and fasten the test tube by a clamp to the ring stand. The test tube should be inclined at an angle of about forty-five degrees.

Invert a bottle of water (best warm) in the pneumatic trough, but do not put the delivery tube into the water until c.

b. Heat the test tube gently with a moving flame. Result? Warm more. Result?

When a steady stream of gas is evolved, hold over the end of the delivery tube a cold and dry beaker. What collects in it?

c. Now put the end of the delivery tube into the pneumatic trough, and fill the collecting bottle with the gas. The gas is nitrous oxide, N2O. Write the equation.

Set the bottle of gas mouth upward and covered upon the table, and then fill a test tube with the gas.

Note.

Be sure to take the delivery tube out of the water before you remove the flame.

d. To the test tube of gas add 5 c.c. cold water, close the tube tightly with the thumb, and shake vigorously. Open the tube under water. Result?

e. What is the odor of the gas in the bottle? Insert into it a pine splinter with a glowing tip. Result? What gas resembles nitrous oxide in its vigorous support of combustion?

EXPERIMENT XXXIX.

PHYSICAL PROPERTIES OF SULPHUR.

Apparatus. Test tubes, filter, funnel, evaporating dish, beaker.

Materials.

Powdered roll sulphur, carbon disulphide.

a. Test the solubility of sulphur as follows: In a test tube shake 1 c.c. powdered roll sulphur with 5 c.c. water; filter, and evaporate the filtrate in an evaporating dish. Result? Conclusion?

What is the odor of sulphur? Its taste?

b. Treat not more than 1 c.c. powdered sulphur in a test tube with 5 c.c. carbon disulphide.

Caution.

Carbon disulphide is inflammable. Do not bring it near a flame.

Close the test tube with the thumb, and shake it thoroughly. Result? Pour the contents of the tube into a small beaker, and set this aside in a gas chamber (not in your cupboard) until the carbon disulphide evaporates. Result? What is the shape of the larger crystals?

c. Fill a test tube one-third full of sulphur, hold it inclined at an angle of about forty-five degrees, and heat it carefully. Note the changes through which the sulphur passes as you raise its temperature.

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What is the color of the liquid formed by melting the sulphur? Is it viscous (thick) or limpid (thin; easily poured)? Pour a drop of it into water. Color of the product? Is it hard or soft? Sulphur melts at about 114° C.

d. What change does the sulphur undergo when you heat it further? Tilt the test tube to an almost horizontal position from time to time until you find the point at which the liquid cannot be poured. Then continue heating, and notice that the sulphur becomes limpid again.

Finally, heat the sulphur to boiling. You will know that boiling is taking place when you see the dark brown liquid condensing upon the upper (cooler) parts of the tube. Sulphur boils at 446° to 448° C.

e. Pour the boiling sulphur into a beaker of cold water. Result? Color of the product? Is it hard or soft? Elastic or brittle? Keep this for several weeks, noting from day to day any changes that take place.

EXPERIMENT XL.

CHEMICAL PROPERTIES OF SULPHUR.

Apparatus. Deflagrating spoon, 250 c.c. bottle, cardboard, test tube.

Materials. Sulphur, blue litmus paper, powdered iron.

a. Put about 1 c.c. powdered sulphur in a deflagrating spoon, heat it in the flame until it burns briskly, and then put the spoon into a bottle of air. Keep the bottle covered with cardboard having a hole in it for the handle of the spoon,

Let the sulphur burn as long as it will. Name the product of the combustion. What is its physical state? Its odor? Try its effect upon wet blue and red litmus papers.

b. Mix in a mortar 5.6 grams powdered iron and 3.2 grams powdered sulphur, and put the mixture into a test tube. Heat the lower portion of the tube for a moment in the Bunsen flame. Result? When action begins, withdraw the test tube from the flame. Describe all that takes place.

c. When the product is cool, break the test tube, and remove the solid lump. Describe the product. It is ferrous sulphide, FeS.

Write the equation for its formation. Save the solid for Experiment XLI.

EXPERIMENT XLI.

HYDROGEN SULPHIDE.

Apparatus. Test tubes, stopper, and delivery tube. Materials. Ferrous sulphide from Experiment XL; dilute sulphuric acid; solutions of cupric sulphate, barium chloride, lead nitrate, cadmium sulphate, sodium hydroxide, and litmus.

Note. Perform this experiment in a gas chamber, or where there is a good draught.

a. Treat the lump of ferrous sulphide made in Experiment XL with dilute sulphuric acid in a test tube. Result? The gas is hydrogen sulphide, H2S. Attach a stopper and delivery tube, and fill a test tube held mouth

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upward with the gas. Apply a match to the test tube. Result? Note odor of the burning gas.

Result?

b. Pass the hydrogen sulphide gas from the generating tube into 5 c.c. dilute cupric sulphate (CuSO4) solution in a test tube. Result? Continue about one minute.

Now see that the delivery tube is clean, and pass the gas three or four minutes into 15 c.c. water in a test tube. Then wash out the generating tube thoroughly.

c. Filter the test tube of cupric sulphate into which you have passed hydrogen sulphide. Compare the color of the filtrate with that of the cupric sulphate taken. Conclusion?

The black residue is cupric sulphide, CuS. Write the equation for the action of hydrogen sulphide upon cupric sulphate.

d. Add a few drops of the hydrogen sulphide solution to 2 c.c. lead nitrate solution, Pb(NO3)2. Result? If the insoluble product is lead sulphide, PbS, write the equation.

Repeat, using cadmium sulphate solution in place of lead nitrate. Result? If the insoluble product is cadmium sulphide, CdS, write the equation.

e. Test the reaction of the hydrogen sulphide solution with red and blue litmus papers. Results? Conclusion? Add to the remainder of the hydrogen sulphide solution 1 c.c. sodium hydroxide solution. The solution now contains sodium sulphide, Na2S. Write the equation.

f. How would you make ammonium sulphide solution, (NH4)2S? Write the equation.