346 PHYSIOLOGICAL CHEMISTRY. 



weak acetic acid to give a slight reaction, and boil. If a precipitate forms, 

 which is rarely the case, albumin is shown. 



With 50 cc. of the liquid make the albumose test. Add to it finely 

 powdered zinc sulphate as long as it dissolves on stirring. On saturating 

 the solution completely a flocculent precipitate gradually settles. This is 

 essentially the " albumose " fraction and may contain a little gelatin. 

 After 24 hours filter, and test the filtrate for peptone by the biuret reac- 

 tion; this is generally negative. 



Use the remainder of the original solution for the recognition of crea- 

 tine. Add to it carefully a solution of basic acetate of lead as long as 

 a precipitate forms. This will carry down phosphates, sulphates and 

 other compounds forming insoluble combinations with it, but not creatine. 

 A slight excess of the lead must be added to insure complete precipitation. 

 This can be determined by allowing the first formed precipitate to settle 

 and adding more reagent as necessary. Finally filter, and remove the 

 excess of lead by passing in hydrogen sulphide. Filter again, and remove 

 as much as possible of the excess of sulphide used, by shaking. Then 

 concentrate the liquid to a small volume by slow evaporation on the water- 

 bath and allow it to stand a day or more in a cool place for crystalliza- 

 tion of the creatine. Pour off the supernatant liquid and wash the fine 

 crystals obtained with a little strong alcohol in which creatine is but 

 slightly soluble. 



Ex. Dissolve the creatine in a little hydrochloric acid and evaporate 

 the solution slowly to dryness on the water-bath. This action converts 

 creatine into creatinine. Dissolve the residue in a little water and divide 

 the solution into two parts. To one add a solution of zinc chloride, 

 which produces a white crystalline precipitate containing the creatinine- 

 zinc chloride, (CJIiNaO^ZnCla. The character of the crystals can be 

 seen under the microscope. To the other part of the solution add a few 

 drops of a dilute solution of sodium nitroprusside and then, drop by drop, 

 dilute solution of sodium hydroxide. This gives a ruby red color which 

 fades to yellow. Add enough acetic acid to change the reaction and 

 warm. The color becomes green and finally blue. This is known as 

 Weyl's reaction. The blue color finally obtained is Prussian blue. 



Ex. The mother liquor left after crystallizing the creatine contains 

 traces of xanthine bases. Add enough ammonia to give an alkaline reac- 

 tion and filter. Then add a few drops of ammoniacal solution of silver 

 nitrate which precipitates the several substances in flocculent form. 



BONE AND GELATIN. 



In the moist bone as it exists in the body the water and 

 solids are, in the mean, in about the proportion of one to two. 

 In very young persons, however, the water is in greater ex- 

 cess, while with age the solids increase. The solid matter 

 consists roughly of i part of organic matter to 2 of mineral. 



