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ANHYDROUS 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 eaused 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 baryta, 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 
