a. Determine whether aluminum is a conductor of heat as in Experiment LXIX, a. Does the wire melt in the Bunsen flame (use tongs)? Try the blast-lamp. Result?

b. To 2 c.c. aluminum filings add 5 c.c. concentrated hydrochloric acid, and warm. Result? Test the gas. Equation?

c. Wash the filings remaining from b, by decantation, add 5 c.c. concentrated sodium hydroxide solution, and warm carefully. Determine the nature of the gas evolved. Result? The solution contains sodium aluminate, NaзAIO3 (cf. Experiment LXV, d). Equation?

d. To 5 c.c. of aluminum sulphate solution, Al2(SO4)3, add 1 c.c. sodium hydroxide solution. Result? Equation? Get half of the precipitate into a second test tube, and add an excess of sodium hydroxide solution. Result? If the solution now contains sodium aluminate, NaзAlO3, write the equation. To the other half of the precipitate add hydrochloric acid. Result? Equation? Compare with this the behavior of zinc hydroxide.

e. Dissolve as much ammonium sulphate as possible in 5 c.c. hot water, and add to it in a beaker 5 c.c. water similarly saturated with aluminum sulphate. Cool the mixture. Result? The product is ammonium alum. Heat again to complete solution, and let stand over night. Result? Shape of crystals?

f. Repeat e, using potassium sulphate instead of ammonium sulphate. Results? Compare the crystals.

g. To 5 c.c. of the solution of any aluminum salt add sodium carbonate solution. Result? Identify the escaping gas. The precipitate is aluminum hydroxide, Al(OH)3. Mix a cubic centimeter of powdered alum

with a cubic centimeter of sodium bicarbonate, and add water. Result?

h. To 1 c.c. of a solution of cochineal add 5 c.c. alum solution, immerse a piece of white muslin, and then add ammonium hydroxide solution, shaking. Results?

EXPERIMENT LXXII.

IRON.

Apparatus. Test tubes, tongs, blast-lamp, magnet, beaker. Materials. - Iron wire and filings, copper wire; hydrochloric, sulphuric, and nitric acids; solutions of potassium ferrocyanide, ferricyanide, and sulphocyanate; ammonia water, hydrogen sulphide, ammonium sulphide, solid ferrous sulphate, and ferric chloride.

a. Compare the heat conductivity of iron wire with that of copper. Test its magnetic properties; its fusibility in the Bunsen flame and the blast-lamp. Results?

b. Treat 3 c.c. iron filings in a beaker with 20 c.c. dilute hydrochloric acid, stirring. Results? Identify the gas. If the solution contains ferrous chloride, FeCl2, write the equation. When action almost ceases, filter off 10 c.c. of the solution. Color of filtrate?

c. Divide the filtrate of b into four parts. To the first add a few drops of potassium ferricyanide solution, KзFe(CN)6. Result? This is "Turnbull's blue." To the second portion add ammonia-water. Result. Equation? Note any change on standing in the air. To the third part add potassium ferrocyanide, K4Fe(CN)6.

Result? To the last portion add potassium sulphocyanate solution, KSCN. Result?

Wash out your test tubes and beakers at once.

d. Filter the remainder of the ferrous chloride solution of b, and add 2 c.c. concentrated nitric acid. Heat carefully for two minutes in a beaker. Resulting color? The solution contains ferric chloride and nitrate. To a drop of it in a test tube add a drop of potassium ferricyanide solution; if it still gives a blue precipitate, add 2 c.c. more nitric acid, and boil again.

Treat the resulting substance in four test tubes with the reagents used in c. Result in each case?

The precipitate from potassium ferrocyanide and a ferric salt is "Prussian blue.”

e. Classify the results of c and d (last part) in five vertical columns.

f. In a test tube shake 2 c.c. powdered ferrous sulphate with 10 c.c. water, pour off half of the solution, and pass hydrogen sulphide into it. Result? Does all the iron appear to be precipitated? Write the equation representing the reaction you would expect to take place. From Experiment XLI tell the phuric acid upon ferrous sulphide. here. Compare these two equations.

effect of dilute sulWrite the equation Conclusion?

To the other half of the ferrous sulphate solution add five drops of dilute sulphuric acid, and pass in hydrogen sulphide. Compare with the result without the acid. Now add ammonium sulphide. Result? Equation?

g. Dissolve 1 c.c. ferric chloride, FeCl3, in 10 c.c. water, and pass in hydrogen sulphide at least two minutes. Result? Boil the contents of the tube, and then filter. Test the filtrate with a drop of potassium ferricyanide solution. Result and conclusion?

Determine the nature of the residue on the filter paper by collecting it on a piece of porcelain and igniting it. Odor?

Write the equation for the action of hydrogen sulphide on ferric chloride.

Apparatus.
Materials.

EXPERIMENT LXXIII.

NICKEL AND COBALT.

Platinum wire, test tubes.

Nickel and cobalt and their nitrates; solutions of the nitrates; borax, sodium hydroxide solution, concentrated, chemically pure hydrochloric acid.

a. Give the physical properties of cobalt and nickel from an examination of the metals. Effect of a magnet? b. To 2 c.c. nickel nitrate solution, Ni(NO3)2, add a drop of hydrochloric acid and then hydrogen sulphide. Result? Now add ammonium sulphide. Result? Equation? Explain the results from Experiments XLI and LXXII, f.

MANGANESE COMPOUNDS.

103

c. Make a borax bead as in Experiment LVIII, a and b, and determine the color given to it by nickel nitrate. d. Repeat b and c with cobalt nitrate, Co(NO3)2, instead of nickel nitrate. Results?

e. To 2 c.c. cobalt nitrate solution add sodium hydroxide solution, a drop at a time, until it is in excess. Results?

f. To 2 c.c. cobalt nitrate solution add 5 c.c. concentrated, chemically pure hydrochloric acid. Result? Dilute with water. Result?

Apparatus.

EXPERIMENT LXXIV.

MANGANESE COMPOUNDS.

Platinum wire, test tubes.

Materials. Manganese sulphate, potassium permanganate, ferrous sulphate, grape-sugar, ammonia-water, hydrogen sulphide, and ammonium sulphide.

a. Dissolve 1 c.c. powdered manganese sulphate, MnSO4, in 5 c.c. water. To half of it add a drop of dilute sulphuric acid and then hydrogen sulphide. Result? Now add ammonium sulphide. Result? Color? Equation? Explain the results.

b. To the other half of solution a add ammoniawater. Result? Equation?

c. To 2 c.c. ferrous sulphate solution (cf. Experiment LXXII, f) add potassium permanganate solution. Result? Continue, drop by drop, until the solution is just faintly pink. Now add ammonia-water. State and explain the result (cf. Experiment XLII, ƒ).