Chemistry and Chemical Arts. 135 
are received over mercury, with a bell-class, containing a strong so- 
lution of potassa. The decomposition being over, the carbonate of 
lead is heated anew, and about as much carbonic acid is liberated as 
before, in order to drive out all the nitrogen, and to force it into the 
bell-glass. After a suitable degree of agitation, the carbonic acid 
will be found to be wholly absorbed, and there will remain only the 
nitrogen, which may be measured with precision. ‘The only pre- 
caution requisite to be taken, consists in decomposing a quantity ca- 
pable of producing at least thirty or forty cent. cubes of nitrogen gas. 
—Idem. 
9. Ovide of Iron an Antidote for Arsenic Acid. (Annalen 
der Physik, 1834, No. 6.)—The following is extracted from a let- 
ter of Dr. Brunsen to M. Poccenvorr, dated Gottingen, May 1, 
1834.—It is some time since I was led to notice the fact that a so- 
lution of arsenic acid is so completely precipitated by the hydrated 
oxide of iron, (perfectly pure, freshly precipitated and suspend- 
ed in water,) that a current of sulphuretted hydrogen introduced into 
the filtered liquor, mingled with a little muriatic acid, reveals no trace 
of arsenic acid. I have ascertained more recently that this same 
substance, mingled with ammonia, and gently digested with arsenic 
acid, previously reduced to an impalpable powder, changes this last 
substance into an insoluble, basic arseniate of iron. A series of ex- 
periments founded upon this observation, convinces me, that this 
body unites the most favorable properties to serve as an antidote of 
the solid arsenic acid, as well as for its solution. Dr. BerrHo xp, at 
my request, had the goodness to unite with me in the investigation 
with the view of submitting the subject, in its full extent to the most 
thorough examination. The results of the investigation have much 
exceeded our expectations, and we are confirmed in the opinion that 
the hydrated oxide of iron is a more efficacious antidote against ar- 
senic acid, whether solid or in solution, than the white of an egg, is 
against the sublimate. 
Young dogs, (not over a foot high) to which we administered 
from four to eight grains of arsenic acid, in the condition of a fine 
powder, (tying up the wind-pipe to prevent vomiting) lived more 
than a week, without giving the least symptom of poisoning by ar- 
senic, neither during life, nor in dissection. The excrements, which 
were slight, because the animals lived without eating or drinking, 
contained almost all the whole of the poison in the state of the basic 
arseniate of iron, but no trace of undecomposed arsenic acid. 
