ADDITIONS AND NOTES TO VOL. II. 541 



Bence Jones* believes that he has convinced himself, by 

 numerous experiments, that after the use of ammoniacal salts (he 

 employed the carbonate, tartrate, and hydrochlorate of ammonia), 

 nitric acid might always be detected in the urine, and consequently 

 that the power of oxidation possessed by the organism is so great, 

 that the nitrogen of the ammonia is oxidised into nitric acid. I 

 regret that this observation must be regarded as so far erroneous, 

 that the method employed by Jones for the discovery of nitric 

 acid must necessarily yield a reaction which is similar to that of 

 nitric acid. Jones decomposed about four ounces of urine with 

 half an ounce of concentrated sulphuric acid, and distilled two- 

 thirds of the fluid in a retort ; in the fluid thus yielded by distil- 

 lation, Jones thought he might determine the amount of nitric or 

 nitrous acid by Price's method (which is a mixture of starch, 

 iodide of potassium, and hydrochloric acid). In some experiments 

 which I made, I certainly found that the distilled fluid, when 

 treated with iodide of potassium and hydrochloric acid, turned 

 starch blue. In the meanwhile it would seem chemically incom- 

 prehensible how nitric acid, if it really were present in the urine, 

 could pass unchanged from it during its distillation with sulphuric 

 acid ; we need only observe that in this concentration of the fluid, 

 the chloride of sodium, as well as the supposed nitrate in the 

 urine, will be decomposed by the sulphuric acid, and that nitrous 

 acid must be formed together with free chlorine, but the former is 

 at once decomposed into nitrogen and water, on being brought in 

 contact with urea ; the undecomposed nitric acid, if any could be 

 present, would also be decomposed on boiling. Now it is easy to 

 see that sulphurous acid, by which, as is well known, hydriodic 

 acid is decomposed, passes into the receiver, and thus probably 

 induces this supposed nitric-acid reaction. The following results 

 were obtained from the experiments which were made in my 

 laboratory by Jafle, one of my students, for the purpose of 

 verifying this proposition : ordinary urine, when no ammoniacai 

 salts had been taken, was found to yield this reaction when treated 

 by Bence Jones's method ; this reaction, however, did not occur 

 when the distillate had stood for some time in the air, in which 

 case the sulphurous acid had become converted into sulphuric acid. 

 The distillate, even after the most careful distillation with sulphuric 

 acid, always yielded, with chloride of barium, a precipitate which 

 was insoluble in acids and much water, but this precipitate is not 

 formed when the urine has been treated with phosphoric instead 

 * Philosophical Transactions. 1851, pp. 399-409. 



