. Kirkes' handbook of physiology . Fig. 308.—TheUrinometer. PHOSPHATES 401 split off from the organic radicle and may be precipitated by the additionof barium chloride in hot solution. 9. Phosphates. The phosphates of urine consist of the earthyand alkaline salts, the latter predominating. Take a 50 sample of urine,add strong ammonia, and heat. The phosphates of calcium and magnesiumseparate out, as they are insoluble in aikaline solution. Filter. To the filtrate add a solution of magnesium sulphate. This precipitatesthe sodium and potassium phosphates as a triple phosphate of magnesium,w
. Kirkes' handbook of physiology . Fig. 308.—TheUrinometer. PHOSPHATES 401 split off from the organic radicle and may be precipitated by the additionof barium chloride in hot solution. 9. Phosphates. The phosphates of urine consist of the earthyand alkaline salts, the latter predominating. Take a 50 sample of urine,add strong ammonia, and heat. The phosphates of calcium and magnesiumseparate out, as they are insoluble in aikaline solution. Filter. To the filtrate add a solution of magnesium sulphate. This precipitatesthe sodium and potassium phosphates as a triple phosphate of magnesium,which is insoluble. Tests for phosphates in general are: Add nitric acid to a sample of urine, warm gently, then add a few dropsof 10 per cent ammonium molybdate; a yellow precipitate of ammoniumphospho-molybdate is formed. Or, add acetic acid, then a few drops of. Fig. 309.—Doremus Ureometer. uranium acetate; a bright yellow precipitate of uranium ammonium phosphateis formed. These two reactions are used as the basis for a quantitative de-termination of phosphorus. 10. The Preparation of Urea. Take 100 of normal urine, evap-orate to one-half its quantity, and precipitate the phosphates and sulphatesby adding a mixed solution of barium hydrate and nitrate. Filter, evaporatethe filtrate to dryness, take up in warm 95 per cent alcohol, and refilter. Crys-tals of urea separate out when the alcohol is evaporated off. Evaporate a large sample, 200 , of urine to a syrupy mass, add nitricacid. Crystals of urea nitrate are formed. Wash the crystals in dilute nitricacid, then dissolve in water. The urea is set free by adding barium carbonate26 402 EXCRETION until the carbon dioxide ceases to come off. Filter, evaporate over a waterbath to dryness, and dissolve the urea in 95 per cent alcohol; decant, and re-crystallize by evaporating off the al
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