Air, water, and food from a sanitary standpoint . The compounds produced by the action of ammonia onmercuric solutions are considered as substitutions of 1 Hgfor 2H in NH4, and are called mercur-ammoniums. Tetra-mercur-ammonium iodide (NHg2I), the compound formed byaddition of the Nessler reagent, is a brown precipitate, sol-uble in excess of KI in the presence of KOH with a brown-ish-yellow color proportional within certain limits to theamount of NH3: NH3 + (2HgI2 + 2KI + 3KOH) = NHg2I + 5KI + 3H2O. The free ammonia in all probability does not exist inthe water in a free state or as the hydro
Air, water, and food from a sanitary standpoint . The compounds produced by the action of ammonia onmercuric solutions are considered as substitutions of 1 Hgfor 2H in NH4, and are called mercur-ammoniums. Tetra-mercur-ammonium iodide (NHg2I), the compound formed byaddition of the Nessler reagent, is a brown precipitate, sol-uble in excess of KI in the presence of KOH with a brown-ish-yellow color proportional within certain limits to theamount of NH3: NH3 + (2HgI2 + 2KI + 3KOH) = NHg2I + 5KI + 3H2O. The free ammonia in all probability does not exist inthe water in a free state or as the hydroxide; it is probablypresent in the form of carbonate or of chloride. When watercontaining these or similar compounds of ammonia is boiled,they are decomposed and free ammonia passes off with the io6 AIR, WATER, AND FOOD. steam and is found in the distillate; hence the origin of thename. Determination of Total Organic Nitrogen by theKjeldahl Process—Directions.—Measure 500 of thewater into a round-bottomed flask of 750 capacity and. Fig. 10.— Apparatus for Distilling Ammonia by Steam. boil until about 200 have been driven off. (The freeammonia which is thus expelled may be determined, if de-sired, by connecting the flask with a condenser.) Allow thewater remaining in the flask to cool, and add 10 ofpure concentrated sulphuric acid free from nitrogen. Mixby shaking; place the flask in an inclined position on wire WATER. ANALYTICAL METHODS. IO7 gauze under the hood and boil cautiously until the water isall driven off. Place a small funnel in the neck of the flaskto prevent the escape of acid fumes, and continue the heatingfor at least half an hour after the sulphuric acid becomeswhite. Meanwhile rinse out the distilling apparatus (seeFig. 10), and free it from ammonia as usual. Then, after theacid in the digestion-flask has cooled, rinse down the neckof the flask with ioo of ammonia-free water and attachthe flask to the distillation apparatus. Add io
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