URINE. 185 



the urine has a decidedly alkaline reaction that nitric acid is 

 preferable for the detection of small quantities of albumen, 

 as in these instances the albumen is held in solution by the free 

 alkali. 



A turbidity may occur on the application of heat from the 

 precipitation of earthy phosphates, or possibly of carbonate of 

 lime, when no albumen is present; but in this case it is directly 

 removed on the addition of nitric acid : similarly, nitric acid 

 may throw down a deposit of uric acid, which may be mistaken 

 for albumen, but in this case no precipitate is caused by the 

 application of heat. Dr. G. O. Rees has observed, that after 

 the use of cubebs or balsam of copaiva, the urine is rendered 

 turbid by nitric acid, although it contains no albumen ; it is, 

 however, not affected by heat. Hence, if there should be a 

 tendency to the deposition of phosphates, a precipitate might 

 ensue both on heating, and on the addition of nitric acid, and 

 yet no albumen be present. I have confirmed the accuracy of 

 the above observation ; the precipitate consists of minute oil- 

 vesicles readily soluble in alcohol, and possessing an odour of 

 balsam of copaiva. 



The quantitative analysis of albumen is best effected by 

 boiling the urine, collecting the albumen on a filter, washing, 

 drying, and weighing it, and ascertaining its weight in relation 

 to that of the urine which was boiled, and to the solid residue. 

 The portion of urine from which the albumen has been separated 

 by boiling, may also be used for the determination of the other 

 solid constituents and of the urea, if the quantity of albumen 

 is not very large, and if the coagulated albumen is carefully 

 washed. If the proportion of albumen is so large as to cause 

 the urine to gelatinize on being heated, which, however, is very 

 seldom the case, it may be feared that the coagulated albumen 

 will entangle many other substances; in that case, the amount 

 of solid constituents may be determined from a fresh quan- 

 tity of urine, about 500 600 grains ; the coagulated albumen 

 must be treated several times with hot water before it is 

 dried. When the quantity of albumen is very small, as for in- 

 stance when the urine becomes only slightly turbid on heating, 

 its amount cannot be determined with accuracy. It is then 

 contained in the water-extract, and it is sufficient to state that 

 the urine contains traces of albumen. If the amount of albu- 



