406 PHOSPHORIC AND SULPHURIC ACIDS. 



large quantities of common salt, but by potash salts also ; it is diminished under 

 the opposite conditions. 



In disease it is greatly diminished ; in pneumonia and other inflammations accompanied by 

 effusions, in continued diarrhoea and profuse sweating, constantly in albuminuria and in 

 dropsies. [In cases of pneumonia, sodic chloride may at a certain stage almost disappear from 

 the urine, and it is a good sign when the chlorides begin to reappear.] In other chronic diseases, 

 the amount of NaCl excreted runs nearly parallel with the amount of urine passed. In condi- 

 tions of excitement the amount of sodic chloride is diminished, and potassic chloride increased; 

 in conditions of depression the reverse is the case (Zculzcr). 



Test. Add to the urine nitric acid and then nitrate of silver solution, which gives a white 

 curdy precipitate of chloride of silver. In albuminous urine the albumin must first be removed. 

 Microscopically look for the step-like forms of common salt, and also for the crystals of sodic 

 chloride and urea ( 256, 4). 



2. Phosphoric acid occurs in urine as acid sodic phosphate and acid calcic and 

 magnesic phosphates to the amount of about 2 grammes daily [30 grains]; it is 

 more abundant after an animal than after a vegetable diet. The amount increases 

 after a mid-day meal until evening, and falls during the night until next day at 

 noon. It is partly derived from the alkaline and earthy phosphates of the food, 

 and partly as a decomposition-product of lecithin and nuclein. As phosphorus is 

 an important constituent of the nervous system, the relative increase of phosphoric 

 acid is due to increased metabolism of the nervous substance. 



Pathological. In fevers, the increased excretion of potassic phosphate is due to a consump- 

 tion of blood and muscle ( 220, 3). It is also increased in inflammation of the brain, soften- 

 ing of the bones, diabetes, and oxaluria ; after the administration of lactic acid, morphia, chloral, 

 or chloroform. It is diminished during pregnancy, owing to the formation of the foetal bones ; 

 also after the use of ether and alcohol, and in inflammation of the kidney. 



[Tests. To urine add nitric acid and solution of ammonium molybdate and boil, a canary- 

 yellow precipitate of ammonium phosphomolybdate indicates the presence of phosphoric acid. 

 Or, add half its volume of caustic potash to urine, and boil. The earthy phosphates are precipi- 

 tated, but not the alkaline phosphates.] 



Earthy phosphates are precipitated by heat in some pathological urines. This 

 precipitate is distinguished from albumin, which is also precipitated by heat, by 

 being soluble in nitric acid, which precipitated albumin is not. [The earthy phos- 

 phates are not precipitated until near the boiling point.] 



Quantitative. The amount of phosphoric acid is estimated by tritation with a standard 

 solution of uranium acetate ; ferrocyanide of potassium being the indicator. The indicator gives 

 a brownish-red colour when there is an excess of free uranium acetate. 



In addition to phosphoric acid, phosphorus occurs in an incompletely oxidised form in the 

 urine, e.g., glycennphosphoric acid ( 251, 2), which occurs to the amount of 15 milligrammes 

 in a litre of urine; it is increased in nervous diseases and after chloroform narcosis.^ 



3. Sulphuric acid occurs in the urine, the greater part in combination with the 

 alkalies, and the remainder united with indol, skatol, and pyrokatechin, in the form 

 of aromatic etliersulphonic compounds, the ratio being 1 : 0*1045. All conditions 

 which favour the formation of indol, skatol, or pyrokatechin, increase the amount 

 of combined sulphuric acid. The total daily amount of sulphuric acid is 2*5 to 3*5 

 grammes [37 to 52 grains]. It is increased by the administration of sulphur, 

 (Krause). The sulphuric acid is chiefly derived from the decomposition of proteids, 

 and hence its amount runs parallel with the amount of urea excreted. The amount 

 of alkaline sulphates in the food is, as a rule, very small. 



An increased excretion of sulphuric acid in fevers indicates an increased metabolism of the 

 tissues of the body. In renal inflammation it has been observed to be diminished, and in 

 eczema it is greatly increased. Feeding with taurin (which contains sulphur), in the case of 

 rabbits, (but not in camivora or man), increases the sulphuric acid in the urine (Salkowski). 

 According to Ziilzer, a copious secretion of bile lessens the relative amount of sulphuric acid in 

 the urine. 



Test. Barium chloride gives a copious white heavy precipitate of barium sulphate, insoluble 

 in nitric acid. 



In addition to sulphuric acid, sulphur (J) occurs in an incompletely oxidised form in the 

 urine (potassium sulphocyanide, cystin, and sulphur-bearing compounds derived from the bile) 



