A Textbook on Applied Chemistry Volume 1 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 edition. Excerpt: ... bromine to 50 cubic centimeters of the acid to color it and boil until color disappears. Proceed as for sulphuric acid. For rapid work, use 10 cubic centimeters of the sample and use the rapid method given above. In either case, deduct the barium sulphate found above from the total and each gram of barium sulphate in excess corresponds to.27-L68 gram of S0, . 3. Arse1zz'c.---The detection and determination of arsenic in hydrochloric acid that is to be used in the preparation of foodstuffs is very important. A very large number of methods for both its qualitative and quantitative determination have been proposed and are in use. The following, however, seem to be the most convenient and exact. ((2) Q22al2'ta2'2'2/2 T es2's.--Take 10 cubic centimeters of the sample in a test tube, dilute with 10 cubic centimeters of distilled Water, carefully pour on the top of the acid 5 cubic centimeters of a freshly prepared hydrogen-sulphide solution, and allow to stand for 1 hour. Prepare a second tube in exactly the same manner and allow to stand for 1 hour in a water bath at from 70 to 80 C. If no precipitate, or yellow ring, appears between the two layers in either case, arsenic is absent. By this method the presence of W milligram of arsenic in the 10 cubic centimeters of acid can be detected. For the most accurate detection of arsenic take 5 liters of the acid, add about-1; gram of potassium chlorate, to prevent the arsenic volatilizing as AsCl, during evaporation, and dilute with water until the specific gravity does not exceed 1.1. Evaporate to dryness in a well-enameled porcelain evaporator, take up the residue in a little water, and test the solution in a Marsh apparatus, which is described in Qualitalive Analysis. (6)...