THE AROMATIC CONSTITUENTS OF THE URINE. 247 



alkaline with milk of lime, and treated with a solution of calcium 

 chloride so long as a precipitate forms. \Yater is then added to the 

 300 c.c. mark. After standing for a while the phosphates are 

 filtered off. The precipitate is washed with a little water. Filtrate 

 and washings are rendered slightly acid with acetic acid, and are 

 then evaporated to a syrup. This is stirred while still warm with 

 about 25 to 30 c.c. of absolute alcohol, transferred to a glass- 

 stoppered flask, and diluted with absolute alcohol to 100 c.c. After 

 twenty-four hours the mixture is filtered. The filtrate is treated 

 with a small amount of sodium acetate in solution, and is con- 

 centrated to about 50 c.c. To this is added 0.5 c.c. of a concentrated 

 alcoholic solution of zinc chloride, which is prepared by dissolving 

 a small amount of the salt in 80 per cent, alcohol, and diluting with 

 95 per cent, alcohol to a specific gravity of 1.2. The mixture is 

 then well stirred and set aside in a cool place for several days. 

 The crystals of the chlorozincate of kreatinin are now collected 

 on a previously weighed filter and washed with alcohol until free 

 from chlorides, when they are dried at 100 C. and weighed. 

 The corresponding amount of kreatinin is ascertained by multiply- 

 ing the weight by 0.6243. The material which is thus obtained 

 is, however, always impure, owing to an admixture of various pig- 

 ments and traces of chlorides. If greater accuracy is required, it is 

 hence necessary to determine the amount of zinc in the crystals, 

 which may be done as follows : the material is covered with a 

 little nitric acid ; the solution is evaporated, the residue incinerated, 

 extracted with water, and the aqueous solution evaporated, the 

 residue ignited, and finally weighed. The zinc is thus obtained as 

 oxide, from which the corresponding amount of kreatinin is cal- 

 culated by multiplying by 2.7790. 



To isolate the kreatinin from the chlorozincate, the latter is dis- 

 solved in a small amount of hot water and boiled for ten minutes 

 with well-washed plumbic hydrate. After filtering off the insoluble 

 oxide of zinc and the chloride of lead the filtrate is evaporated to 

 dryness and extracted with cold absolute alcohol. This takes up 

 the kreatinin, while a small amount of kreatin formed during the 

 process of boiling remains. On evaporation the kreatinin is obtained 

 in crystalline form, and can be further purified by recrystallization 

 from water. 



THE AROMATIC CONSTITUENTS OF THE URINE. 



It has been pointed out in a preceding chapter that during the 

 process of intestinal putrefaction various aromatic bodies are formed 

 from the albumins of the food or their products of digestion, and 

 are then absorbed and eliminated in the urine, either as such or in 

 combination with sulphuric acid, glucuronic acid, or glycocoll. 

 Some of these bodies, such as indol and skatol, may be regarded as 

 specific products of putrefaction ; while others or closely related 



