=182. Kjeldahl Method as Practiced by the Holland Royal Experiment Station.=—_Necessary Reagents_: 1. Phosphosulfuric acid, made by mixing a liter of sulfuric acid of specific gravity 1.84 with 200 grams of phosphoric anhydrid: 2. Alkaline sodium sulfid solution, made by dissolving 500 grams of sodium hydroxid and six grams of sodium sulfid or eight and one-half grams of potassium sulfid, in a liter of water: 3. Mercury: 4. Paraffin in small pieces: 5. Dilute sulfuric acid and dilute potash solution, both of known strength: 6. Pieces of previously ignited pumice stone or of granulated zinc: 7. Neutral solution of rosolic acid or litmus. _Apparatus_: The apparatus necessary consists of oxidation flasks of about 200 cubic centimeters capacity and distillation flasks of about 500 cubic centimeters capacity, both of bohemian glass. Copper may be used for the distillation flasks.[152] _The Process_: A gram of the sample to be analyzed is placed in an oxidation flask together with twenty cubic centimeters of phosphosulfuric acid and a drop of mercury, about 600 milligrams, and heated till the fluid becomes colorless. After cooling, dilute and wash the contents of the flask into a distillation flask. The resulting volume should be about 300 cubic centimeters. Add 100 cubic centimeters of the alkaline sodium sulfid solution and some pieces of ignited pumice stone or granulated zinc. Distill the ammonia, receiving the distillate in a flask containing a known volume of the standard sulfuric acid. Titrate with tenth-normal potash, using litmus or rosolic acid as indicator.