186 THE SECRETIONS: 



men is very considerable, certain changes must be made in the 

 method of determining the other constituents. The albumen 

 itself must be always separated by boiling. 



In determining the urea we must see whether, when the 

 albumen is very abundant, the greater quantity of it cannot be 

 precipitated by alcohol. The albumen thus separated must be 

 washed with alcohol. If we were to attempt to determine the 

 urea in very albuminous urine in the manner described in page 

 136, there would be reason to apprehend that the albumen pre- 

 cipitated by the application of heat would entangle too large an 

 amount of urea. 



The determination of the uric acid is usually regarded as 

 very uncertain in strongly albuminous urine. I have, however, 

 convinced myself that this constituent may be separated from 

 very albuminous urine by the careful addition of extremely di- 

 luted hydrochloric acid, [or acetic acid may be used, which 

 precipitates uric acid without affecting the albumen.] It must 

 also be observed that urine which is very rich in albumen always 

 contains only mere traces of uric acid, and a very small pro- 

 portion of urea. 



In the determination of the water-extract, it must be borne 

 in mind that albumen is present in it. As its quantity is 

 known, it must be subtracted from the combustible portion of 

 the water-extract. 



The spirit-extract is obtained from the portion of urine pre- 

 cipitated by alcohol, where it occurs in a state of solution. 

 This solution must be filtered, evaporated, and all substances 

 insoluble in anhydrous alcohol precipitated by the addition of 

 that reagent. These are spirit -extract with chloride of sodium, 

 and a certain quantity of albumen which remains insoluble on 

 the addition of water. The watery solution of the spirit-ex- 

 tract and of the salts must be filtered, again evaporated, weighed, 

 and then treated in the manner described in page 137. 



If we wish to avail ourselves of the alcoholic solution which 

 remains after the precipitation of the spirit-extract by anhydrous 

 alcohol, for the estimation of urea, we must take another por- 

 tion of urine for the determination of the alcohol-extract and 

 ammonia-compounds, and proceed in the same manner as for 

 the determination of the urea. 



In the determination of the fixed salts it must be remembered 



