URINE. 181 



cipitated, in which the predominating character is the forked 

 arrangement of the crystals. Fig. 30 b exhibits the forms in 

 which the phosphate of lime appears. 



The quantitative determination of earthy-phosphate sedi- 

 ments presents no difficulty, if other constituents are not also 

 present. The method of proceeding is exactly the same as for 

 the quantitative determination of the urate-of-ammonia sediment 

 in page 176. Its amount must be determined in reference to the 

 whole quantity of urine, and to the amount of solid residue. 



In order to separate the earthy phosphates from urates, and 

 mucus or pus, the sediment must be collected, washed with 

 a weak solution of ammonia, the earthy phosphates taken up 

 by water acidulated with hydrochloric acid, precipitated from 

 the filtered solution by free ammonia, collected on a filter, dried, 

 and weighed. Upon submitting the dried precipitate to a strong 

 heat the ammonia is given off, and the weight proportionally 

 diminished. The ratio of the earthy phosphates to the solid 

 residue of the urine enables us to determine whether an increase 

 in this particular class of constituents has occurred. If the re- 

 lative quantities of phosphate of lime and ammoniaco-magnesian 

 phosphate are required, the separation must be conducted on the 

 principles described in page 139. 



(3. Diminution of the earthy phosphates. There can be no 

 doubt that in certain diseases the earthy phosphates are much 

 diminished, and that occasionally they altogether disappear. If 

 the amount of earthy phosphates in the urine should be so slight 

 that, upon the addition of free ammonia no precipitate is ob- 

 served, it will be necessary, in order to be assured of the entire 

 absence of this constituent, to evaporate a large quantity of 

 urine, to incinerate the solid residue, to dissolve the ash in 

 water containing a little nitric acid, and then to add ammonia. 

 If no precipitate is formed after the fluid has been warmed and 

 allowed to rest for some hours, the absence of earthy phosphates 

 may be considered as proved. 



b. Increase or diminution of the chloride of sodium and of the 

 fixed alkaline sulphates and phosphates. 



The quantity of fixed alkaline salts almost always decreases 



