time to time. Result?

flame. Result?

Result? Heat it again in the oxidizing

d. Boric Acid. Dissolve 5 grams powdered borax in 10 c.c. hot water, and add 10 c.c. concentrated hydrochloric acid. Set aside until next laboratory period. Result? The product is boric acid, HBO3. Filter off the crystals, wash them on the filter with a little cold water, and dry them on fresh filter paper.

e. Dissolve the crystals of boric acid in hot water, and add the solution to a lump of sodium carbonate.

Result?

EXPERIMENT LIX.

SODIUM COMPOUNDS.

Apparatus. Test tubes, stopper and delivery tube, magnifying glass, platinum wire, watch glass or glass slip.

Materials. Sodium bicarbonate, lime-water, sodium carbonate (solid and in solution), sodium chloride, calcium chloride, barium chloride, sodium nitrate and sulphate, hydrochloric acid.

a. Refer to Experiment XII for the properties of sodium and its action on water.

b. Heat 2 c.c. powdered sodium bicarbonate carefully in a test tube having a delivery tube that passes into lime-water. Result? Result? Is there any other volatile product? When no more gas is evolved (do not melt the test tube), let the product in the tube cool, and then add 2 c.c. cold water. Note the temperature effect. Compare with this the action of anhydrous sodium carbonate

POTASSIUM COMPOUNDS.

85

upon water. What are the products formed by heating sodium bicarbonate? Equation?

c. Heat 2 c.c. sodium chloride with 5 c.c. water in a test tube; filter; and let some of the filtrate evaporate completely on a glass slip or a watch glass. Examine the crystals with a magnifying glass, if possible. Their shape?

d. Dissolve a small piece of calcium chloride, CaCl2, in 5 c.c. water, and add sodium carbonate solution. Result? Repeat, using barium chloride instead of calcium chloride. Result? Write the equations.

e. Dip a platinum wire with a glass holder (cf. Experiment LVIII, a) into 5 c.c. concentrated hydrochloric acid in a test tube, and then heat the wire in the Bunsen flame until the flame remains colorless. If necessary, dip the wire more than once. Now wet the clean wire with the acid, dip it into powdered sodium chloride, and heat it. Effect on the flame?

f. Clean the wire and repeat e, using sodium nitrate instead of sodium chloride. Repeat again with sodium sulphate. What color do sodium salts give to the flame?

EXPERIMENT LX.

POTASSIUM COMPOUNDS.

Apparatus. Watch glass, iron dish, test tubes, beaker or evaporating dish, platinum wire, copper wire.

Materials. Potassium chloride, sodium nitrate, sulphur, barium chloride solution, potassium hydrogen tartrate, limewater, dilute sulphuric acid, concentrated hydrochloric acid, potassium nitrate, and potassium sulphate.

a. Heat 8 grams of potassium chloride and 10 grams of sodium nitrate with 20 grams of water until there is complete solution, and boil off half of the water over the wire gauze? Result? Let the precipitate settle and pour the solution into a test tube. Wash the residue with

5 c.c. cold water, and then dissolve it in the smallest possible amount of hot water. Pour a few drops of the solution in a watch glass and set aside. Result? Compare the crystals with those obtained in Experiment LIX, Conclusion?

C.

What happens in the test tube containing the original solution? The visible product is potassium nitrate, KNO3.

b. Mix 3 c.c. powdered potassium nitrate on a clean piece of paper with 1 c.c. powdered sulphur, and pour the mixture, at arm's length, upon a hot iron dish (use no wire gauze). Result? Let the product cool, boil it with 10 c.c. water in a test tube, and add to 5 c.c. of it barium chloride solution. Result? See Experiment XLIV, b. What is the product of the deflagration of potassium nitrate and sulphur?

c. Heat an iron dish red hot, and pour upon it 3 c.c. powdered potassium hydrogen tartrate, KHC4H4O6 (cream of tartar). Results? Color of residue? Heat it five minutes longer at red heat, pressing the mass down with a glass rod occasionally. When the dish is cool, treat the residue in a test tube with dilute sulphuric acid. After all evolution of gas ceases, identify the gas by placing in the mouth of the tube a looped copper wire holding a drop of lime-water. What remains undissolved? What substance would you find in plant ashes if the plants contained potassium salts of organic acids?

DISTINCTIONS BETWEEN METALS.

87

d. Clean a platinum wire as in Experiment LIX, e; dip it into strong hydrochloric acid, and then into powdered potassium chloride, and heat it in the flame. Result? Repeat, using potassium nitrate instead of the chloride. Use the sulphate. Results? Results? What color do potassium compounds give to the flame?

EXPERIMENT LXI.

AMMONIUM AMALGAM. DISTINCTIONS BETWEEN THE ALKALI METALS.

Materials. Ammonium chloride, sodium amalgam, sodium and potassium chlorides, tartaric acid, two unknown substances.

a. Dissolve 2 c.c. ammonium chloride in 5 c.c. water, and add a piece of sodium amalgam (Na+Hg). Results? The product is ammonium amalgam. Note what happens to it. Odor? Reaction of solution?

Note.

Do not throw away the resulting mercury, but ask what to do with it.

b. Add 5 c.c. water to 3 c.c. powdered potassium chloride and shake thoroughly. Pour off the solution and add to it 5 c.c. of a concentrated solution of tartaric acid, H2C4H4O6. Make this by shaking 5 c.c. powdered tartaric acid with 15 c.c. water. Wait for result. Result? The product is potassium hydrogen tartrate. Equation?

c. Repeat b, using sodium chloride in place of potassium chloride. Result? Repeat again, using ammonium chloride in place of potassium chloride. Result?

d. From Experiment XXXIII, b and c, tell what happens when ammonium salts are treated with alkalies. How distinguish between sodium salts on the one hand and ammonium and potassium salts on the other? Between sodium salts and potassium salts (two ways)?

e. Get from the instructor two unknown substances, and determine if they are salts of sodium, potassium, or ammonium.

EXPERIMENT LXII.

CALCIUM.

Apparatus. Triangle of iron wire, ring stand, blast-lamp, evaporating dish, platinum wire, and coin.

Materials. Lumps of marble, lime-water, red litmus paper, old mortar, plaster of Paris, paper, calcium chloride, calcium sulphate, and ammonium carbonate solution.

a. Touch a piece of wet red litmus paper with a piece of marble. Result? Result? Support a lump of marble about 5 c.c. in volume on a triangle of iron wire laid upon a ring of the ring stand, and heat the marble ten to fifteen minutes in the hottest Bunsen flame — in a blastlamp, if possible. When the marble is cold, touch wet, red litmus with the part that was heated. Result? Explain. What products are formed when marble is heated (cf. Experiment XLVIII, b)?

Slake about 5 c.c. of quicklime by adding to it water, drop by drop, as long as the water is taken up readily. Wait for the result, and describe it. Is there a temperature effect? Equation?