383 Intelligence and Miscellaneous Articles. 



the stomach a large quantity of ammoniacal compounds, nitric acid 

 appears in the urine as a product of their oxidation. 



From the extreme apparent improbability that such an oxidation 

 could be effected in the animal organism, and at the instigation of 

 Prof. Lehmann, the author has repeated the experiments upon which 

 this inference is founded; and has come to the conclusion, that the 

 method which Dr. Bence Jones adopted for detecting the presence 

 of nitric acid in the urine is altogether inapplicable, and consequently 

 that the inference that ammonia is oxidized within the organism is 

 perfectly unfounded. 



The method consists in distilling the somewhat concentrated urine 

 with concentrated sulphuric acid until about one-half or two-thirds 

 have passed over, treating the distillate with carbonate of potash, 

 evaporating and testing the residue for nitric acid by means of starch, 

 iodide of potassium and dilute hydrochloric acid, or with indigo. 



The author believes that this process is inapplicable, because, 

 even admitting the presence of nitric acid, it would appear impos- 

 sible to distil over this acid in the presence of urea, or indeed any 

 other organic substance. In order to decide this point, the author 

 added a few drops of nitric acid to normal urine, concentrated by 

 evaporation, and then distilled with sulphuric acid. The distillate, 

 treated with starch and iodide of potassium, gave a reaction, which, 

 although readily accounted for by subsequent experiments, at first 

 led the author to form the erroneous opinion that a distillation of 

 undecomposed nitric acid from urine actually took place. Normal 

 urine, distilled with concentrated sulphuric acid, gave a liquid which 

 became intensely blue when treated with starch and iodide of 

 potassium, while at the same time it gave no indication of nitric 

 acid with protosulphate of iron. It soon became evident that this 

 reaction was altogether owing to the presence of sulphurous acid, 

 formed by the action of the sulphuric acid upon the organic sub- 

 stances, and which, as is well known, causes a separation of iodine. 

 It thus becomes easily intelligible why Dr. Bence Jones so seldom 

 obtained this reaction in normal urine, as he saturated the distillate 

 with carbonate of potash, and evaporated. 



The presence of sulphurous acid in the distillate, and thedependence 

 of the reaction upon it, was demonstrated in the following manner : — 



In the first instance, normal urine was distilled without any addi- 

 tion of acid ; and, as was to be expected, the distillate gave no re- 

 action. Normal urine was then distilled with sulphuric acid ; the 

 distillate gave a reaction with starch and iodide of potassium ; when 

 tested with protochloride of tin for sulphurous acid, it acquired a 

 yellow colour, but even on boiling no precipitate was formed, a 

 result which might fairly be attributed to the small quantity of sul- 

 phurous acid. In order to prove more decisively that the reaction 

 was owing to this small quantity of sulphurous acid, normal urine 

 was distilled with phosphoric instead of sulphuric acid; and the 

 distillate when tested did not give the slightest trace of a reaction. 

 Lastly, when a distillate which at first gave the reaction was allowed 

 to stand twenty-four fours, it no longer gave it, but the presence of 

 sulphuric acid could be distinctly ascertained. 



