468 PHYSIOLOGICAL CHEMISTRY. 



whatever in its detection, as heat will precipitate it from an acid, 

 neutral, or sometimes even alkaline urine ; the precipitate should, 

 however, always be tested by the addition of a few drops of nitric 

 acid, and the previous addition of a few drops of acetic acid is also 

 advisable. 



A neutral urine should never be acidified by nitric acid (instead of 

 acetic acid), because a drop or two of nitric acid may in some cases 

 prevent the coagulation of albumin by heat, though a larger quantity 

 (10 to 20 drops) has no such effect. 



Quantitative estimation of albumin. The average amount of 

 albumin present in acute cases of albuminuria is 0.1 to 0.5 per cent., 

 rarely over 1 per cent., though it may rise to 4 per cent. 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 twelve (or better for twenty-four) 

 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 twelve or twenty- 

 four hours scarcely any albumin has collected at the bottom, there is 

 said to be a trace. 



The volumes of coagulated albumin indicate the following quantities of dry 

 albumin : 



Slight turbidity indicates about 0.01 per cent. 



sV of the tube is filled 0.05 " 



T V ... ... o.io 



\ " " 0.25 " 



J " 0.50 



" " 1.00 " 



Complete coagulation . . . . . 2 to 3 " 



A better method of exactly estimating the amount of albumin is 

 its complete separation and weighing, as described below. 



Experiment 76. Acidify 100 c.c. of clear albuminous urine with acetic acid ; 

 heat to the boiling-point in a, water-bath for half an hour, and filter through a 

 small filter, previously dried at 110 C. (230 F.) and weighed; wash with boil- 

 ing water to which a little ammonia water has been added (to remove uric acid 

 and urates), then with pure water until the filtrate is not rendered turbid any 

 longer by silver nitrate, next with pure alcohol, and finally with ether. Dry 

 and filter contents at 110 C. (230 F.) and weigh. 



As it may happen that the precipitated albumin encloses earthy phosphates, 



