70 ON URINE AND ITS ACIDS. 



fee phospho- failed to yield phosphoric acid : I was under the necessity 



ric acid. . ., _ 



therefore of adopting the synthetical method. Accordingly 

 after having saturated by means of potash the extract of 

 some urine, thnt I had evaporated to dryness with the pre- 

 ; cautions already described, I poured in a little vinegar, 

 treated it with alcohol, and obtained the same results us { 

 have already related; that is to say, the portion, that was 

 not dissolved after repeated affusions of alcohol, was acid. 

 This proof, I am aware, may still be questioned : for, if the 

 phosphoric acid existed in the urine, it would be partly re- 

 tained by the salts present in it, in the same manner as the 

 acetous, and would become insoluble in alcohol. But if it 

 be considered, that the existence of the acetous acid in 

 urine appears certain*; that nothing demonstrates the pre- 

 sence of the phosphoric; that the greater part of the free 

 acid of the urine evaporated to the consistence of a sirup 

 dissolves in alcohol; and that all this acid, thus dissolved, is 

 the acetous : lastly, if we recollect, that the residuum is 

 slightly acid ; and that, if saturated with potash, afterward 

 acidulated with vinegar, and treated afresh with alcohol, it 

 remains equally acid: all these circumstances compared to- 

 gether, I conceive, will acquire such a degree of certainty, 

 as absolutely to convince us, that it is the acetous acid alone 

 in Urine which dissolves the phosphate of lime, and which 

 alone too most commonly imparts to it the property of red- 

 dening infusion of litmus. 

 Farther proof But, to render this last conclusion still more evident, X 

 that it is the ought to demonstrate, more directly than has hitherto been 

 done, that the benzoic acid is not in fact a constant princi- 

 ple of urine. For this, instead of employing sublimation 

 with or without an excess of another acid, when the urine 

 is reduced to a sirupy consistence; a method always inaccu- 

 rate, since the benzoic acid combined with ammonia is car- 



* I believe, that, in the evaporation of the urine in a water hath, a 

 little litee is decomposed, and that ammonia, and peihaps a little ace- 

 tous acid is formed. Supposing this to he the ease, it still remains very 

 probable, that the acid of urine is the acetous acid, and r*ot any other :, 

 for in favour of this opinion 1 might not only adduce the reasons that 

 have been, or that will be given, but even the tendency the uree would 

 have in this case to be converted into acetous acid. 



ried 



