1813.] Chemical Properties of Animal Fluids. 417 



The sulphuric acid is also found in urine. The alkaline fluids 

 merely neutralized by acetic or muriatic acid, and then mixed 

 with muriate of barytes, give no indication of sulphuric acid. 

 But if the residue left after the evaporation of these fluids be first 

 calcined, and the saline part then extracted by lixiviating the 

 ash, and treated with muriatic acid and muriate of barytes, a 

 notable quantity of sulphuric acid is found, produced from the 

 sulphur contained in animal matter. But with urine the appear- 

 ances are very different. Muriate of barytes added to it forms 

 immediately a copious precipitate of sulphate of barytes ; and I 

 have constantly found that the quantity of sulphuric acid in urine 

 exceeds that of the phosphoric acid. Rouelle, the elder, long ago 

 detected sulphuric acid in urine, but this was considered as an 

 accidental circumstance : I have however very good reason for 

 supposing this acid to be a most essential constituent part of 

 urine. The production of this acid takes place in the kidneys, 

 and the action of these organs resembles combustion in this 

 respect, that part of the constituent elements of the urine, such 

 as the sulphur, phosphorus, the radicals of the alkalies and 

 earths, &c. become oxidated to their maximum : and here also 

 the kidneys generate some acids with compound bases. The 

 remainder of the blood gives rise to the urea, which, being 

 formed from the materials of the blood, ought to contain more 

 azote in proportion as a greater number of the other elements of 

 these materials has been acidified. It would however be incor- 

 rect to consider the production of urine as an excretion of the 

 azote which is in excess in the animal economy, because it 

 appears that the amount of its quantity in the constituents of 

 urine is not greater than in the constituents of blood. We might 

 with as much reason consider the kidney as an organ for oxida- 

 tion : but it is certainly an error to believe that any organ except 

 the lungs has the office of removing one particular element in a 

 greater proportion than the rest. 



I at first conceived that the whole of the sulphur contained in 

 the blood was acidified in the kidneys, and consequently imagined 

 that the same change might be induced on a part of the azote, 

 the carbon, and the hydrogen. Proust asserts that the urine 

 contains carbonic acid ; but it is very difficult to establish the 

 certainty of this fact, because the urea is decomposed by a heat 

 even inferior to that of boiling water, and produces carbonate of 

 ammonia, which is decomposed by the free acid of the urine, 

 and carbonic acid is disengaged. I am rather disposed to believe 

 that urine does not contain carbonic acid, because no bubbfeg of 

 air are ever seen to form on the sides of the containing vessels: 

 and if urine still warm be thrown on any Substance whatever 

 reduced to powder, such as powdered sugar, no effervescence 

 Vol. II. N° VI. 2 D 



