386 PHYSIOLOGICAL CHEMISTRY. 



Quantitative estimation of albumin. An approximate method for 

 the comparative estimation of albumin is to precipitate it (with 

 the precautions above given) in a graduated test-tube by heat 

 and setting aside for 11 (or better for 24) hours. At the end of 

 that time the proportion of the coagulated albumin which has 

 collected at the bottom of the fluid is noticed. If the albumin 

 occupy one-fourth, one-sixth, one-tenth of the height of the 

 liquid, there is said to be one-fourth, one-sixth, or one-tenth of 

 albumin in the urine. If, however, at the end of 12 or 24 

 hours scarcely any albumin has collected at the bottom, there 

 is said to be a trace. 



A better method of exactly estimating the amount of albumin 

 is to collect the precipitate on a small filter, previously dried at 

 100 and weighed. After having been well washed, the filter 

 and contents are dried and weighed. As it may happen that 

 the precipitated albumin encloses earthy phosphates, it is well to 

 burn filter with contents in a platinum crucible, and to deduct 

 the weight of the remaining inorganic residue from that of the 

 albumin. 



Detection of sugar. Traces of sugar, or as much as 0.01 per 

 cent., are said to occur normally in urine, and are of no signifi- 

 cance ; moreover, it is as yet doubtful whether these traces of 

 sugar are actually present in normal urine. Large quantities 

 of sugar are often indicated by a high specific gravity of the 

 urine, which then varies from 1030 to 1050. 



Of the many tests by which sugar. may be detected in urine 

 three only will be mentioned; they are generally known as the 

 copper tests (also termed Trommer's or Fehling's test, according to 

 the manner in which the reaction is conducted), the bismuth test, 

 and the fermentation test. The copper tests as well as the bismuth 

 test are based upon the deoxidizing or reducing power which 

 grape-sugar possesses for many metallic oxides such as cupric, 

 bismuthic, and silver oxide, which, in the presence of alkalies, 

 are converted into the lower state of oxidation, or are reduced 

 to metals. 



The tests for sugar should always be preceded by tests for 

 albumin, which latter, if present, should be removed by coagu- 

 lation and filtration. 



