APPENDIX D.

TREATMENT OF PLATINUM RESIDUES.

THESE residues generally contain the platinum as double chloride of potassium or ammonium. Any soluble platinum chloride is precipitated by addition of ammonium chloride, and the filtered precipitate is dried and ignited. The residue is then thoroughly washed with hot water, and dissolved by boiling with a mixture of three parts of hydrochloric to one of nitric acid. It is best to pour off the solution from time to time and add fresh acids. When all the platinum is dissolved the solution is evaporated nearly to dryness; hydrochloric acid is added (to expel the nitric acid), and the liquid is evaporated to complete dryness on the water bath. The residue is dissolved in water or preserved dry in bottles.

QUESTIONS AND EXERCISES.

3. (a) How many grams of oxygen can be obtained by heating 1,080 grams of mercuric oxide ?

(6) Twenty-four grams of oxygen are required; how much mercuric oxide must be heated?

4. (a) What is left when potassium chlorate is heated?

(b) How many grams of potassium chlorate must be heated in order to yield 500 grams oxygen ?

(c) How much potassium chloride will remain after heating 247 grams potassium chlorate?

5. How is potassium chlorate distinguished from potassium chloride?

6. (a) Describe the best means of preparing oxygen?

(b) The residue in a flask used to prepare oxygen, consisted of 13 grams of potassium chloride; how much chlorate had been heated, and how much oxygen evolved?

(c) Why is manganese dioxide mixed with potassium chlorate in preparing oxygen?

8. (a) What happens when a taper is burned in oxygen?

(6) How is the presence of carbon dioxide generally ascertained?

9. (a) 14 gram of charcoal containing 96 per cent. of carbon is burnt in oxygen; how much carbon dioxide is produced?

(b) Contrast the burning of a candle with the breathing of an animal in air.

10. How much oxygen is required to burn 42 grams of sulphur to sulphur dioxide?

11. How much phosphoric anhydride can be obtained by burning 2°34 grams phosphorus in oxygen, and how much phosphoric acid would be obtained by dissolving the anhydride in water?

13. (a) How much hydrogen can be got by dissolving 15 ounces of zinc in sulphuric acid?

(b) Which will yield the greater quantity of hydrogen when dissolved in acids-162 grams zinc, or 140 grams iron? Why?

14. How much water will be formed by burning all the hydrogen evolved by dissolving 3'42 grams zinc in sulphuric acid?

15. How much zinc sulphate should be got by dissolving I lb. zinc in sulphuric acid?

19. How is nitrogen prepared?

21. One hundred grams of potassium nitrate are heated with sulphuric acid; how much nitric acid and hydrogen potassium sulphate will be obtained?

22. What are the best tests for nitric acid?

24. (a) How is ammonia gas prepared, and what is the residue from its preparation?

(6) How much ammonium chloride must be used to obtain 291 grams ammonia gas?

25. How is ammonia tested for?

27. (a) How is ammonium nitrate prepared?

(6) How much ammonium nitrate can be got from 327 grams of nitric acid?

28. How much nitrous oxide can be obtained from 437 grams of ammonium nitrate ?

29. How can nitrous oxide be distinguished from oxygen?

30. If 7 grams of copper be acted on with nitric acid, how much nitric oxide will be obtained, and how much copper nitrate will remain ?

31. Mention some of the properties of nitric oxide. 32. (a) How is carbon dioxide prepared from marble?

(6) How much hydrochloric acid will be needed exactly to decompose a kilogram of marble?

33. What reaction takes place when carbon dioxide and lime-water are brought together? Give the equation.

34. (a) How is carbon monoxide prepared from formic acid, and from oxalic acid?

(b) How much carbon monoxide should be obtained from 12 grams oxalic acid?

35. What happens when a mixture of carbon monoxide and dioxide is shaken up with caustic soda?

M

36. (a) Give the equation for the preparation of chlorine from common salt, manganese dioxide, and sulphuric acid?

(6) What is the action of hydrochloric acid on manganese dioxide?

(c) How much chlorine can be got by heating 560 grams manganese dioxide with salt and sulphuric acid? (d) How much can be got by heating the same quantity with hydrochloric acid ?

37. (a) Mention the chief properties of chlorine. (b) How does chlorine act as a bleaching agent? 38. How much common salt is needed to prepare 109 kilograms of hydrochloric acid?

39. (a) What is meant by neutralizing” an acid

solution?

(b) What is meant by the terms "acids," "bases," and "salts"?

40. (a) Give the equation for the preparation of bleaching powder from lime and chlorine.

(b) How much chlorine is needed to convert 5 tons of slaked lime into bleaching powder?

41. (a) What happens when each of the following acids is brought in contact with calcium hypochlorite, sulphuric, nitric and hydrochloric?

(6) How can a solution of hypochlorous acid be distinguished from a solution of chlorine?

42. (a) Give the equation for the preparation of iodine from potassium iodide.

(b) Thirty-seven grams of iodine were obtained; how much potassium iodide was used?