26. What volume of aluminium (▲ 2·6) must be dissolved in potassium hydrate to make a litre of hydrogen at 12° C. ?

Al, + 2HKO + 2H,O=2KA10, +3H,.

27. If 10 grams of aluminium sulphide are thrown into water, what volume of hydrogen sulphide at 15° C. and 800 m.m. is given off?

28. Find a formula for Stourbridge fire-clay which contains silica 64.1 per cent., alumina 23.15 per cent., ferrous oxide 1.85 per cent., magnesia 0.95 per cent., and water 10 per cent.

CHAPTER XXVIII.

MAGNESIUM. Mg = 24.

1. How much magnesium is there in 1000 grams of (a) magnesite MgCO,, and (B) Epsom salts MgSO,.7H,0?

2. How many yards of wire inch in diameter can be made from an ounce of magnesium (A 1-74)?

3.

What volume of oxygen is required to burn 4 grams of magnesium?

Mg +0 = MgO.

4. 10 grams of magnesium are dissolved in hydrogen chloride, what volume of hydrogen is given off?

Mg + 2HCl = MgCl ̧ + H ̧.

5. 100 grams of potassium are heated with magnesium chloride, how much magnesium is formed?

6. 40 grams of magnesite are dissolved in hydrogen chloride, what volume of carbon dioxide is given off?

MgCO, + 2HCl=MgCl,+H,O + CO

7. 10 grams of magnesite are dissolved in acid, what volume of carbon dioxide at 26° C. is evolved?

MgCO,+2HCl=MgCl, + H,O + CO

2

8. A dolomite contains 12 per cent. of magnesium carbonate, how many kilograms of Epsom salts could be made from 120 kilograms of it?

MgCO ̧ + H2SO̟ ̧ + 6H2O = CO2 + MgSO̟ ̧ . 7H ̧O.

4

2

2

4

9. Find the percentage composition of magnesium pyrophosphate (Mg,P,0,).

10. Find the percentage composition of meerschaum (MgSiO4H0).

11. Find the percentage composition of dolomite (CaMg2CO2).

12. Find the percentage composition of serpentine (Mg,Si,O,. 2H2O).

2 7

13. How much crystallized magnesium sulphate can be obtained by dissolving 1000 grams of magnesite in dilute hydrogen sulphate, and what volume of carbon dioxide is evolved?

MgCO2+ H2SO2+ 6H ̧O = MÁSO ̧ . 7H2O + CO2.

4

2

4

2

14. What masses of (a) sodium Na,CO,, (B) calcium CaCO3, and (7) magnesium MgCO, carbonates contain one litre of carbon dioxide?

15. 40 grams of magnesium are dissolved in dilute hydrogen chloride, what volume of hydrogen at 21° C. and 380 m.m. is given off?

Mg + 2HCl = MgCl2 + H2.

16. Equal masses of magnesium (A 1-7), zinc (A 7), and cadmium (▲ 8·5) are alloyed. If no change of volume takes place, find the density of the alloy.

17. Equal masses of magnesium (▲ 1·7), and of cadmium (▲ 8·5) are fused together. If no change of volume takes place, find the density of the alloy.

18. 4 grams of dolomite when strongly heated gave 938 6 c.c. of carbon dioxide. Find the percentage of calcium and of magnesium carbonate in the dolomite ?

CaCOg = CaO + CO

MgCO2 = MgO + CO2.

19. 0-2 gram of magnesium, when dissolved in acid. gave 195.5 c.c. of hydrogen at 13° C. What is the atomic weight of magnesium?

Mg + 2HCl = MgCl, + H,.

20. 0.1 gram of magnesium when dissolved in acid gave 100 c.c. of hydrogen at 12° C. the barometer standing at 758.8 m.m., and the column of water in the tube being 250 m.m. Find the equivalent of magnesium.

mg + h cl = mg cl+h.

21. What volume of hydrogen at 13° C. and 740 m.m. is given off on dissolving 0·02 grams of magnesium in dilute acid?

Mg + 2HCl = MgCl ̧ + H ̧.

22. 2 grams of magnesium are prepared by the electrolysis of the fused chloride, what volume of chlorine at 15o C. and 745 m.m. is given off?

MgCl = Mg + Cl ̧.

23. What volume of nitrogen at 20° C. and 780 m.m. will combine with 50 grams of magnesium?

3Mg + 2N = Mg,N,

24. What volume of hydrogen measured over water at 14o C. and 760 m.m. is set free on dissolving 0.2 grams of magnesium in acid?

Mg + 2HCl = MgCl ̧ + H ̧.

CHAPTER XXIX.

ZINC. Zn. = 65.

CADMIUM. Cd = 112.

1. FIND the percentage composition of (a) zinc blende ZnS and (B) calamine ZnCO2

2. Zinc melts at 773° F. and boils at 1904° F., what are these temperatures on the Centigrade scale?

3. Find the formula of a substance containing zinc 54.17 per cent., silicon 11.67 per cent., oxygen 26.67 per cent., and water 7.5 per cent.

4. How much zinc white can be made from 1000 grams of zinc, and what volume of air is required?

5. 20 grams of zinc are dissolved in dilute hydrogen sulphate, what volume of hydrogen is given off?

6. Find the percentage composition of cadmium sulphide CdS.

7. How much cadmium iodide can be made from 56 grams of cadmium?

Cd + 21 = CdI ̧.