HYDROCHLORIC A CID. 
6 33 
calcium phosphide is found in star-shaped masses of fine prisms (stellar 
phosphate) (Fig. 58). 
Pathologically, a diminution of the urinary phosphates is seen in nephritis 
(Partly), and an increase is said to occur in certain nervous diseases. The 
phosphates may be greatly increased in diahetes insipidus. 
For the estimation of phosphoric acid the urine is first treated with acetic 
acid and sodium acetate, and is then titrated with a standard solution of 
uranium nitrate. Ferrocyanide of potassium or cochineal tincture may be used 
as an indicator to mark the end point of the titration. 
Hydrochloric acid. — There can be little doubt that the greater 
part of the hydrochloric acid of urine exists as sodium chloride, and it 
Fig. 5S. — A. Stellar phosphates ; B. Triple phosphates. 
certainly arises mainly from the common salt present in the food. The 
tissues and fluids of the body maintain a very constant content of sodium 
chloride, any excess is at once excreted, and any diminution in the 
supply immediately reduces the excretion. The amount in the urine 
depends, therefore, in normal circumstances, almost entirely upon the 
quantity ingested, and falls to a minimum during starvation, or when 
a salt-free diet is taken. Pathologically, striking alterations in the 
chlorides of the urine may be observed. Thus, whenever considerable 
exudations occur, as in pneumonic processes, or where pleuritic effusion 
is taking place, the consequent removal of chlorides from the blood may 
lead almost to a cessation of their excretion ; and conversely, during the 
reabsorption of such exudations, the urinary chlorides may considerably 
increase, even when but little salt is being taken by the mouth. Apart 
from such exudations, fever appears to have a specific effect in pro- 
