25S 
NORDH AUSEN SULPHURIC ACID AS A REAGENT. 
of a small quantity of sulphurous acid, from the reaction of 
strong sulphuric acid on the animal matter? The addition of 
water causes a decrease of action of the acid on the organic 
substances contained in the urine. 
The presence of sulphurous acid in the sulphuric acid of 
Nordhausen should equally cause its rejection when operating 
with Marsh's apparatus, since MM. Fordos and Gelis have 
demonstrated that sulphurous acid is, under these circum- 
stances, converted into hydrosulphuric acid, which precipi- 
tates the arsenic as solphuret, and diminishes, although it 
does not completely prevent, the production of the arsenical 
spots. We, however, know that the Nordhausen acid is re- 
commended in preference for this purpose, because it never 
contains arsenic. 
In conclusion: the sulphuric acid of Nordhausen or 
Saxony, used as a reagent in place of the ordinary acid, 
may become, in many chemical researches, a cause of se- 
rious error. This inconvenience results from this acid 
usually containing sulphurous acid. 
Journ. de Pharm. atid de Chim. 
