i9ii] Carl L. Aisberg 119 



take place, nor can the milky mixture be filtered for quantitative 

 purposes by any o£ the ordinary methods. 



Previous investigators used other precipitants such as ferric 

 chlorid, tannic acid, copper sulfate, etc. For our purpose these 

 were objectionable because they precipitate not alone the casein and 

 other proteins present, but their immediate digestion products as 

 well. This leaves too little nitrogen in the filtrate for reliable 

 analytic results. 



These difficulties are obviated by the use of the larger amounts 

 of acetic acid, as above indicated. 



The Estimation of Creatin 



STANLEY R. BENEDICT 



{Cornell University Medical College, New York City.). 



Twenty c.c. of urine (or a volume equal to twice the amount 

 which will be required for an accurate Creatinine reading) is 

 treated with 20 c.c. of approximately normal hydrochloric acid and 

 the mixture boiled nearly to dryness in a beaker or open flask. 

 After the mixture has almost reached dryness it is placed in a boil- 

 ing-water bath, and allowed to remain there for about five minutes 

 after the residue is approximately dry. With the aid of warm 

 water the residue is then washed into a 50 c.c. Volumetrie flask, 

 the mixture cooled, and 5c.c. of 8 to 10 per cent. basic lead 

 acetate Solution added, and the mixture diluted to exactly 50 c.c, 

 and mixed by shaking. The mixture is filtered through a dry 

 filter into a dry beaker and 25 c.c. of the filtrate used for the 

 colorimetric determination as in Folin's process, save that 6 c.c. 

 of 10 per cent. alkali are employed, which should best contain 

 also 5 per cent. of Rochelle salt. This process has the great advan- 

 tage that in the conversion of the creatin less pigment is produced 

 than in former methods. 



