416 Chemical Properties of Animal Fluids. [Dkc : 



2. Urine. 



We possess many analyses of urine, both in a healthy and 

 diseased state, but none of them gives a very extended view of 

 the subject ; and it is clear that the analysis of morbid urine 

 acquires its chief interest from being able to compare it with 

 that of health. 



A. The Acids of the Urine. — The acidity of healthy urine has 

 generally been attributed to the phosphoric acid. By the che- 

 mical change which the blood undergoes in the kidneys, a large 

 portion of its constituent parts are acidified ; so that the blood 

 which enters alkaline into the renal arteries, returns from the 

 renal vessels loaded with many acids, some of which did not at 

 all exist in the blood at its entrance, and others were present in 

 very minute quantity only. The acids of the urine which do not 

 at all exist in the blood are the sulphuric, uric, and sometimes 

 the benzoic ; the others are the phosphoric and lactic. The 

 muriatic and fluoric acids appear to pass from the blood to the 

 urine without increase in their proportional quantity. As by the 

 laws of chemical affinity these acids will unite with any alkali 

 that may be present, and saturate themselves with it in the order 

 of the force of their respective affinities, it must follow that 

 where the quantity of alkali is insufficient to saturate all the 

 acids present, the weakest acids must be those that will remain 

 uncombined and will give the urine its acid properties. These 

 therefore must be the lactic and the uric. 



It is so generally known and so fully proved that the urine 

 contains the phosphoric, muriatic, and uric acids, that it is useless 

 to add any thing further on this subject. 



Urine contains the fluoric acid. In my analysis of bones I 

 have found that human and ox bone contain as much as two per 

 cent, of fluate of lime. It is therefore natural to suppose that 

 the earthy phosphates dissolved in urine, which are chiefly de- 

 rived from the decomposition and absorption of bone, should 

 also retain the same proportion of fluate of lime. To prove it, I 

 precipitated a large quantity of urine with caustic ammonia, 

 collected and calcined the precipitate, mixed an ounce of it with 

 as much sulphuric acid, and then heated the mixture moderately 

 in a platina crucible covered with a glass plate prepared for 

 etching. After some hours I removed the glass, took off the 

 graver's wax, and found the lines corroded by the fluoric acid 

 vapour. 



Urine satUiMed by ammonia, filtered, and mixed with muriate 

 of lime, gives also a gooi' deal of phosphate of lime, containing 

 no fluoric acid. The urine therefore contains no other fluate 

 than that of lime. 



