Laboratory Studies in Chemistry

This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1912. Not illustrated. Excerpt: ... OXYGEN IN POTASSIUM CHLORATE 115 Divide the weight of the zinc by the atomic weight of zinc, and that of the chlorine by the atomic weight of chlorine. You will obtain decimal fractions which will, however, be seen to bear to each other approximately the relation of small whole numbers. These are the numbers which must be added to the symbols to give the formula. An example of the calculation is given in the textbook, page 385. EXERCISE 82 PERCENTAGE OF OXYGEN IN POTASSIUM CHLORATE (Quantitative) Apparatus. -- Pipestem triangle. Porclain crucible with cover. Balance. Small test tubes. Materials. -- Potassium chlorate. Potassium chloride. Silver nitrate solution. Distilled water. Method. -- The oxygen is driven off by heat and the loss in weight obtained. KC1O3->KCl + 3 O. Dissolve 0.2 c.c. potassium chlorate in 5 c.c. distilled water. In another tube, dissolve 0.2 c.c. potassium chloride in 5 c.c. distilled water. Add ten drops silver nitrate solution to each tube. Results? Potassium chlorate is apt to contain a trace of potassium chloride, so that a slight precipitate may be obtained in the first tube also. Weigh crucible, with cover, place the cover on the balance pan beside the crucible, and weigh in the crucible 1 gram of potassium chlorate. Heat carefully for ten minutes, keeping flame in motion; apply the full heat of the burner for five minutes more, cool and weigh without removing cover. Calculate the percentage of oxygen, and compare it with that calculated from the formula. Examine the residue in the crucible. What is it? Dissolve it in water and add silver nitrate solution. Result? EXERCISE 83 THE EFFECT OF HEAT AND OF ACIDS ON CARBONATES Apparatus. -- Wire gauze. Hard glass test tube with one-hole rubber stopper aud delivery tube bent at right ang...