URINE. 



277 



about only after continuous boiling with an excess of the copper salt. 

 Creatinine does not reduce alkaline bismuth solutions and therefore 

 does not interfere with Nylander's and Boettger's tests. 



FIG. 90. 



CREATININE. 



It has recently been shown by Folin that the absolute quantity of 

 creatinine eliminated in the urine on a meat-free diet is a constant 

 quantity different for different individuals, but wholly independ- 

 ent of quantitative changes in the total amount of nitrogen elimin- 

 ated. Shaffer has very recently confirmed these findings and has 

 shown that the output of creatinine under these conditions is con- 

 stant from hour to hour as well as from day to day. 



EXPERIMENTS ON CREATININE. 



i. Separation from the Urine. Place 250 c.c. of urine in a 

 casserole or beaker, render it alkaline with milk of lime and then 

 add CaCl 2 solution until the phosphates are completely precipitated. 

 Filter off the precipitate, render the filtrate slightly acid with acetic 

 acid and evaporate it to a syrup. While still warm this syrup is 

 treated with about 50 c.c. of 95-97 per cent alcohol and the mix- 

 ture allowed to stand 8-12 hours in a cool place. The precipitate 

 is now filtered off and the filtrate treated with a little sodium acetate 

 and about one-half c.c. of acid-free zinc chloride solution having a 

 specific gravity of 1.2. This mixture is stirred thoroughly and 

 allowed to stand in a cold place for 48-72 hours. Creatinme- 

 zinc chloride (Fig. 91, p. 278) will crystallize out under these con- 



