Royal Society. %\% 



In a third experiment, three ounces of urine with a grain and a half 

 of nitre were distilled with three drachms of glacial phosphoric acid ; 

 the distillate neutralized and evaporated gave no trace of nitrous 

 acid; the same urine with the same quantity of nitre and three 

 drachms of sulphuric acid, when distilled, gave a distillate, which 

 when neutralized and evaporated gave decided evidence of nitrous 

 acid. 



In my former paper I showed that by distilling with sulphuric 

 acid when only one-tenth of a grain of nitre was added to each 

 ounce of urine, nitrous acid could be detected. 



From these experiments it appears that distillation with sulphuric 

 acid is to be preferred to distillation with phosphoric acid ; but even 

 with this last acid, when a grain of nitre is added to an ounce of 

 urine, the nitrous acid can be detected. 



I then endeavoured, by using phosphoric instead of sulphuric acid 

 in distilling urine passed after a salt of ammonia had been taken 

 into the stomach, to detect nitrous acid in the urine. 



Two drachms of muriate of ammonia were taken in seven ounces 

 of distilled water. The urine was collected for six hours afterwards. 

 Twelve ounces of this urine were distilled with one ounce of phos- 

 phoric acid (anhydrous). The distillate, when concentrated, did not 

 give any evidence of nitrous acid by Price's test. 



The same experiment was repeated with no better result. 



In another experiment, sulphuric acid, six drachms to twelve 

 ounces of urine, was used instead of phosphoric acid. The distillate 

 as soon as it was obtained gave the slightest precipitate with chloride 

 of barium insoluble in nitric acid, showing that a trace of sulphuric 

 acid was carried over into the receiver. The distillate was made 

 alkaline with pure carbonate of soda, evaporated, and nitrous acid 

 was immediately detected by the indigo and iron test, as well as by 

 Price's test. A portion of the distillate left exposed to the air, on 

 the following day had lost the power of liberating iodine. This 

 arose from the nitrous acid passing into nitric acid. 



Pure nitre gives no colour with starch, iodide of potassium and 

 dilute hydrochloric acid, b';t when fused it produces the liberation 

 of iodine immediately. If the solution of fused nitre is exposed to 

 the air it loses this property, but regains it when the solution is 

 evaporated to dryness and refused and again dissolved. 



In another experiment six ounces of urine passed before the mu- 

 riate of ammonia was taken were distilled with half an ounce of sul- 

 phuric acid, the distillate was highly acid, and gave a slight preci- 

 pitate with chloride of barium ; it was made slightly alkaline, eva- 

 porated to a smr.'l residue, and then gave no evidence of nitrous 

 acid. Then two drachms of muriate of ammonia were taken in seven 

 ounces of distilled water, eight ounces of urine passed four hours 

 afterwards were distilled with half an ounce of sulphuric acid. The 

 distillate was fractional ; the first portion gave no colour with starch 

 test ; it contained a minute trace of sulphurous acid. The second 

 portion was highly acid ; it was made slightly alkaline, evaporated 

 nearly to dryness, and then gave most positive evidence of nitrous 



