(4). Mercuric-oxide, HgO, prepared in the wet way. That prepared from mercury nitrate cannot safely be used. (5). Potassium permanganate tolerably finely pulverized. (6). Granulated zinc. (7). A solution of 40 grams of commercial potassium-sulphide in one liter of water. (8). A saturated solution of sodium-hydrate, free from nitrates which are sometimes added in the process of manufacture to destroy organic matter and improve the color of the product. (9). Solution of cochineal, prepared according to Fresenius Quantitative Analysis, second American edition, page 679. (10). Burettes should be calibrated in all cases by the user. (11). Digestion flasks of hard, and moderately thick, well-annealed glass, which should be about 9 inches long, with a round, pear-shaped bottom, having a maximum diameter of 2½ inches and tapering out gradually in a long neck, which is three-fourths of an inch in diameter at the narrowest part and flared a little at the edge. The total capacity is 225 to 250 cubic centimeters. (12). Distillation flasks of ordinary shape, 550 cubic centimeters capacity, and fitted with rubber stoppers, and a bulb tube above to prevent the possibility of sodium-hydrate being carried over mechanically during distillation; this is adjusted to the tube of the condenser by a rubber tube. (13). A condenser with tube of block tin is best, as glass is decomposed by steam and ammonia vapor, and will give up alkali enough to impair accuracy; the tank should be made of copper, supported by wooden frame, so that its bottom is 11 inches above the workbench on which it stands. It should be about 16 inches high, 32 inches long, and 3 inches wide, gradually widening 6 inches toward the top; the water-supply tube should extend to the bottom, and there should be a larger overflow pipe above.