f. Recall Experiment XXVI for the reaction of salt with litmus. For the reaction of sodium carbonate. Try the action of aluminum chloride solution with red and blue litmus paper. Complete the equations,

For which of these three reactions do you get no evidence from the behavior with litmus? Of what reaction is hydrolysis the reverse? Why is it so incomplete as compared with its reverse?

g. Replacement. To 5 c.c. cupric sulphate solution in a test tube add several small iron nails (brads) and let stand over night. Result? What change has occurred in the color of the solution. What is the precipitate?

Write the equation.

Repeat, using mercurous nitrate (HgNO3) solution with copper turnings. Equation?

Repeat again, with strips of zinc, or granulated zinc, and silver nitrate solution. Result and equation? Compare the results with the action of a metal on an acid, as in Experiment VIII.

EXPERIMENT XXXII.

NITROGEN.

Apparatus. 100 c.c. flask, wire gauze, ring stand, clamp, stopper, delivery tube, pneumatic trough, collecting bottle. Materials. Sodium nitrite, NaNO2; ammonium chloride, NHẠC.

a. Support a flask by means of a clamp about its neck, and place under it the wire gauze. Put into the flask 5 c.c. powdered sodium nitrite, 5 c.c. ammonium chloride, and 50 c.c. water.

Attach the stopper and delivery tube; the delivery tube extends to a pneumatic trough containing water and an inverted collecting bottle full of water.

b. Have ready your evaporating dish full of cold water. Heat the flask gently until a regular but not too rapid stream of gas escapes. If at any time during the heating the evolution of gas (nitrogen) becomes violent, remove the delivery tube from the water, take away the flame and wire gauze, and bring the evaporating dish of cold water up over the bottom of the flask. Let two test tubes of gas escape (why?); then fill the bottle with it.

c. Determine the odor and color of the gas, also its relation to combustion.

Write the equations for the stages of the reaction; also the complete equation.

EXPERIMENT XXXIII.

AMMONIA.

Apparatus. Mortar and pestle, stirring rod, test tubes, 100 c.c. flask, stopper, two right-angle tubes, collecting bottles, gauze.

Materials. Glue, quicklime, litmus, hydrochloric acid, ammonium chloride, ammonium nitrate, ammonium sulphate, sodium hydroxide solution, potassium hydroxide solution.

a. Mix in a mortar about one half gram glue and 2 grams quicklime, and heat the mixture in a test tube. Hold in the mouth of the tube, without touching the tube, a piece of moist blue litmus paper. Red litmus paper. A glass rod which has been dipped into concentrated hydrochloric acid. Results? Note odor. What is it?

b. To about one half gram ammonium chloride in a test tube add 2 c.c. ten per cent sodium hydroxide. solution, and warm gently. Odor? Effect of gas on litmus? On a rod wet with concentrated hydrochloric acid?

c. Repeat b, using ammonium nitrate and sodium hydroxide solution. Results? Use ammonium sulphate and ten per cent potassium hydroxide solution. Results?

The gas formed in the above cases is ammonia, NH3.

d. In a 100 c.c. flask mix 10 grams powdered ammonium chloride and 20 grams powdered quicklime. Odor? Support the flask on wire gauze and attach the stopper and a delivery tube bent twice at right angles (see Experiment XXI, a). Have the second rightangled tube turned upward. On a small ring fastened high up on the ring stand, lay a piece of cardboard with a small hole in it; through the hole pass the delivery tube, and invert over the delivery tube the dry receiver (bottle) intended to collect the ammonia.

e. Heat very gently.

When the bottle is full of gas,

test this by waving air from the bottle toward the nose, cover it and place it mouth down upon the table. Fill three bottles with the gas. Now turn the end of the delivery tube down, so that it just touches the surface of 10 c.c. water in a test tube.

After a minute raise the test tube carefully about 2 cm. Do the bubbles of ammonia rise to the surface of the water? Why? Lower the test tube again until the delivery tube just touches the water, and continue heating the flask gently three minutes. Remove the test tube; and then extinguish the flame. cool not in contact with the wire gauze or any conductor. Why?

Let the flask

f. Did you notice any change in the temperature of the water of the test tube? Explain. Save this liquid.

g. From the method of collecting the gas compare its specific gravity with that of air. Is there any evidence of water in the generating flask?

h. Test the gas in the first receiver with litmus paper keep mouth of receiver down. Test relation of this gas to combustion. Results?

Thrust up into the receiver a glass rod which has been dipped in concentrated nitric acid. Results? The smoke is ammonium nitrate, NH4NO3. Write the equation.

i. Place the second bottle mouth downward in a pan of water. Result? Explain.

j. Warm the bottom and sides of a clean, dry bottle (having a mouth of the same size as that of the third bottle of ammonia) by moving it quickly to and fro in the Bunsen flame; put into it five drops concentrated hydrochloric acid, and place over the bottle of hydrochloric acid gas thus obtained, the bottle of ammonia. Hold the mouths of the bottles firmly together and reverse their positions, so that the ammonia bottle is below the other. Results? What is the product?

k. Examine the solution of ammonia made in e.

What effect has it upon litmus? Hold a piece of moist red litmus about 2 cm. above the solution. Result? Explain.

Put 5 c.c. of the solution into a beaker, note the odor, and let beaker stand for twenty-four hours. Is the odor as strong as before? Inference?

1. Put about 5 c.c. of the ammonia solution of e into an evaporating dish, and boil it gently for five minutes. Compare odor after boiling with that of some of the original solution.

m. Heat a small amount of ammonium chloride for some time on a piece of porcelain or on platinum. Result? n. Write the equations for the reactions which took place in b, c, d, and e, as double decomposition equations; then show the dissociation of ammonium hydroxide.

EXPERIMENT XXXIV.

NITRIC ACID.

Apparatus. 100 c.c. flask, cork stopper, delivery tube (in one piece), test tube, beaker, wire gauze, ring stand.

Materials. Potassium nitrate, concentrated sulphuric and nitric acids, white silk thread, indigo solution, ferrous ammonium sulphate or ferrous sulphate, and copper nitrate.

a. Use apparatus of Experiment XI, Fig. 96. Into the flask put 5 g. potassium nitrate and 10 c.c. concentrated sulphuric acid. Attach the stopper and the delivery tube. The delivery tube must be in one piece without rubber connections. Put the end of the delivery tube