REAGENTS AND APPARATUS
(1). Hydrochloric acid whose absolute strength has been determined.
(a). By precipitating with silver nitrate and weighing the silver chloride.
(b). By sodium carbonate, as described in Fresenius Quantitative Analysis, second American edition, page 680.
(c). by determining the amount neutralized by the distillate from a weighed quantity of pure ammonium-chloride boiled with an excess of sodium-hydrate.
(2). Standard ammonia whose strength relative to the acid has been accurately determined.
(3). C. P. sulphuric acid specific gravity 1.83, free from nitrates, and also from ammonium sulphates, which are sometimes added in the process of manufacture to destroy oxides of nitrogen.
(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.
The block tin condensing tubes should be about ⅜ of an inch inner measure and seven in number, entering the tank through holes in the front side of it near the top above the level of the overflow, and pass down perpendicularly through the tank and out through the rubber stoppers, tightly fitted into holes in the bottom; they should project 1½ inches below the bottom of the tank, and connect by short rubber tubes, with glass bulb tubes, of the usual shape, which dip into glass precipitating beakers. These beakers should project about 6½ inches high by 3 inches in diameter below, gradually narrowing above, and should be about 500 cubic centimeters capacity. The titration can be made directly in them. The seven distillation flasks should be supported on a sheet-iron shelf attached to the wooden frame which supports the tank at the front; where each flask is to stand, a circular hole should be cut with three projecting lips to support the wire gauze under the flask, and three other lips to hold the flask in place, and to prevent its moving laterally out of place while distillation is going on. Below the sheet-iron shelf should be a metal tube carrying seven Bunsen burners, each with a stopcock like those of a gas combustion furnace. These burners are of larger diameter at the top, which prevents smoking when covered with fine gauze to prevent the flame from striking back.
(14). The stand for holding the digestion flask should consist of a pan of sheet iron, 29 inches long by 8 inches wide, on the front of which is fastened a shelf of sheet iron as long as the pan, 5 inches wide and 4 inches high. In this are cut six holes 1⅝ inches in diameter. At the back of the pan is a stout wire running lengthwise of the stand, 8 inches high, with a bend or depression opposite each hole in the shelf. The digestion flask rests with its lower part over a hole in the shelf and its neck in one of the depressions in the wire frame, which holds it securely in position, and heat should be supplied with Bunsen burners below the shelf.