THE INORGANIC CONSTITUENTS OF URINE. 



87 



or the crystalline condition, when it is known as "stellar 

 phosphate" 



(b.) Prepare " stellar phosphate " crystals by adding 

 some calcium chloride to normal urine, and then nearly 

 neutralising. On standing, crystals exactly like the rare 

 clinical form of stellar phosphate are obtained. 



(c.) Triple phosphate or ammonio-magnesic phosphate 

 never occurs in normal urine, and when it does occur, indi- 

 cates the decomposition of urea to give the ammonia 

 necessary to combine with magnesic phosphate to form this 

 compound. It forms large, 

 clear "knife-rest" crystals 

 (Fig. 18.) 



(d.) If ammonia be added 

 to urine, the ammonio-mag- 

 nesic phosphate is thrown 

 down in a feathery form, 

 which is very rarely met 

 with in the investigation of 

 human urine clinically. 



10. General Rules for all Volu- 

 metric Processes. 



(a.) The burette must be 

 carefully washed out with 

 the titrating solution, and 

 must be fixed vertically in a suitable holder. 



Fig. 18. Various forms of triple 

 phosphate. 



(6.) All air-bubbles must be removed from the burette as 

 well as from the outflow tube. The latter must be quite 

 filled with the titrating solution 



(c.) Fill the burette with the solution up to zero, and 

 always remove the funnel with which it is filled. 



(d.) Read off the burette always in the same manner, and 

 always allow a short time to elapse before doing so, in order 

 to allow the fluid to run down the sides of the tube. 



(e.) The titrating fluid and the fluid being titrated must 

 always be thoroughly well mixed. 



