INORGANIC CONSTITUENTS. 441 



When the urine becomes alkaline, whether as a result of 

 the decomposition of urea and the formation of ammonium car- 

 bonate or by the addition of ammonia, the earthy phosphates are 

 precipitated. From alkaline decomposing urine, crystals of 

 ammonio-magnesium phosphate, magnesium ammonium phosphate, 

 or triple phosphates, by all of which names they are known, are 

 deposited. The chemical formula of this deposit is NH 4 MgPO 4 

 -f 6H 2 O. It forms coffin-lid crystals or star-shaped figures. 



Urine that is slightly acid deposits star-shaped masses of 

 prisms of calcium phosphate, called from the form of the crystals 

 stellar phosphates. 



Sulphates. Only a small quantity of the sulphates comes from 

 the food, most of it being the result of the metabolism of the 

 proteids of the body, into which sulphur enters as a component 

 part. These salts occur in the urine in two forms : (1) Inorganic 

 sulphates and (2) ethereal or conjugated suJphates. The total amount 

 of sulphates daily excreted in the urine varies from 1.5 grams to 

 3 grams, of which about one-tenth is in the form of the conjugated 

 sulphates. The conjugated sulphates consist of radicles derived 

 from the aromatic substances present in the urine, joined with 

 sulphuric acid, from which fact they derive their name. Among 

 the most important of the ethereal sulphates are phenol-potassium 

 sulphate and indoxyl-potassium sulphate : besides these are kresol- 

 potassium sulphate, skatoxyl -potassium sulphate, etc. These 

 salts are increased when the putrefaction of proteid substances in 

 the intestines is increased. Whenever, therefore, the amount of 

 sulphuric acid in the urine is increased, it may be due to an in- 

 creased amount of sulphates in the food or drink, or to increased 

 putrefaction in the intestines. 



There is, according to Hopkins, also some sulphur in the urine 

 in the form of neutral sulphur, as contradistinguished from the 

 " acid sulphur " of the sulphates. It is in a less oxidized form 

 than the sulphates, but what the compounds are is not known. It 

 is said that one-fifth of the total sulphur of the urine is in this 

 form. Some of this may come from the taurin of the bile. 



Carbonates. When the urine is alkaline, sodium, calcium, mag- 

 nesium, and ammonium carbonates are present. These are espe- 

 cially abundant after a vegetable diet, for the reason that the 

 malates, tartrates, and citrates contained in such food are con- 

 verted into carbonates, which are eliminated by the kidneys. 

 Carbonic acid also exists in acid urines, as much as 50 c.c. per 

 liter having been found present. 



