402 Mr. Faraday on the mutual Action of Sulphuric Acid 
A portion of the pure salt was prepared and dried for some 
hours on the sand bath, at a temperature about 212°. Known 
weights were then heated in a platinum crucible to dissipate 
and burn off the combustible matter; and the residuum being 
moistened with sulphuric acid to decompose any sulphuret of 
barium formed, was heated to convert it into a pure sulphate 
of baryta. The results obtained were very constant, and 
amounted to 41°714 of sulphate of baryta per cent of salt used, 
equivalent to 27°57 baryta per cent. 
Other portions of the salt were decomposed by being heated 
in a flask with strong nitro-muriatic acid, so as to liberate the 
sulphuric acid from the carbon and hydrogen present, and yet 
retain it in the state of acid. Muriate of baryta was then 
added, the whole evaporated to dryness, heated red-hot, washed 
with dilute muriatic acid to remove the baryta uncombined 
with sulphuric acid, and the sulphate collected, dried, and 
weighed. The results were inconstant; but the sulphate of 
baryta obtained, always much surpassed that furnished by the 
former method. Judging from this circumstance that the sul- 
phuric acid in the salt was more than an equivalent for the 
baryta present, many processes were devised for the determina- 
tion of its quantity, but were rejected in consequence of diffi- 
culties and imperfections, arising, principally, from the pre- 
sence and action of so much carbonaceous matter. The fol- 
lowing was ultimately adopted. 
A quantity of per-oxide of copper was prepared by heating 
copper plates in air and scaling them. A sufficient quantity 
of pure muriatic and nitric acids was provided, and also a 
specimen of pure native carbonate of baryta. Seven grains of 
the salt to be examined were then mixed with seven grains of 
the pulverized carbonate of baryta, and afterwards with 312 
grains of the oxide of copper. The mixture being put into a 
glass tube was successively heated throughout its mass, the 
gas liberated being passed through a mixture of baryta water 
and solution of muriate of baryta. It was found that no sul- 
phurous or sulphuric acids came off, or indeed sulphur in any 
state. The contents of the tube were then dissolved in an ex- 
cess of nitric and muriatic acids, above that required to take 
up all that was soluble; and a little solution of muriate of 
baryta was added for the sake of greater certainty. A por- 
tion of sulphate of baryta remained undissolved, equivalent to 
the sulphuric acid of the salt experimented upon, with that 
contained accidentally in the oxide of copper acids, &c. ‘This 
sulphate was collected, washed, dried and weighed. Similar 
quantities of the carbonate of baryta and oxide of copper were 
then dissolved. in as much of the nitric and muriatic acids as 
was 
