ANHYDROUA SULPHURIC AND SULPHUROUS ACIDS. 445 



bottle, which by a ground stopper could be rendered air-tight. The 

 small bottle containing the weighed portion, and without the stopper, 

 was fastened by a platina wire, and thus quickly introduced into the 

 large bottle, which was then immediately closed, but in such a manner 

 that the fluids themselves could not act upon each other, but only their 

 vapours. After some time I agitated this carefully, but in such a man- 

 ner that only a little of the compound in the small bottle was thrown out 

 and could mix with the nitric acid, which always caused a very strong 

 action, though never the evolution of light. If, on the contrary, by 

 shaking the bottles, a little nitric acid fell into the small bottle, a cry- 

 stalline deposit was formed, which I have not examined more closely, 

 but which perhaps may be the same as that which is often formed 

 during the preparation of the English oil of vitriol, and which consists 

 of sulphuric and nitrous acids and water. After the mixture of the 

 nitric acid and the substance was completed, the whole was diluted 

 with water, and then saturated with a solution of chloride of barium. 



From the quantity of sulphuric acid which was contained in the 

 sulphate of baryta thus obtained, I could easily appreciate the relative 

 proportions of the sulphuric and sulphurous acids in the compound ; 

 for what the first contained more than the latter in weight, could only 

 consist in oxygen which the compound had absorbed. 



But in two experiments, both conducted with equal care, I obtained 

 from the sulphate of baryta less sulphuric acid than I had taken in 

 weight of the compound ; a proof that evidently only a part of the sul- 

 phurous acid had been oxidized by the nitric acid. 



In the first experiment 2*237 grammes of the compound gave 5*633 

 grammes of sulphate of barj^ta, which contained 1*936 of sulphuric 

 acid, equal to 82*08 per cent, of the compound. In the second expe- 

 riment I obtained, from 1 *250 grammes of the compound procured by 

 another preparation, 3*443 grammes of sulphate of baryta, which con- 

 tained 1*1834 grammes of sulphuric acid, indicating 94*67 per cent. 

 of the compound. 



This very slight difference shows plainly that it only arises from the 

 mode of preparation, and that in the combination fuming nitric acid did 

 not convert the free sulphurous into sulphuric acid. Perhaps it might 

 have been effected had more dilute nitric acid been employed, because in 

 the preparation of the English oil of vitriol the sulphurous can convert 

 itself into sulphuric acid ; but for a quantitative analysis it did not seem 

 to me so fitting. Moreover the compound, oxidized by nitric acid 

 and then diluted with water, did not smell of sulphurous acid. That 

 the nitric acid did not fully oxidize the sulphurous acid in the com- 

 pound is evident from the result of a third experiment, in which I took 

 some of the compound which had been oxidized by fuming nitric 

 acid, and having mixed it with a weighed quantity of freshly heated 



2h 2 



