( 154 ) 
Akt. XXVIII. — Some addlitonal facts relating to the habitudes 
of the Hyposulphurous Acid^ and its union with Metallic 
Decides By el. F. W. Herschel, Esq. F. R. S. Com- 
municated by the Author. 
In order to procure the hyposulphite of silver in a state of 
purity, it is not enough to precipitate a solution of silver by a 
neutral hyposulphite. This, as I have shewn in a former com- 
munication, gives a mixture of the salt with sulphuret of silver. 
Nitrate of silver, somewhat diluted, must be poured into a pretty 
strong solution of hyposulphite of soda. A copious precipitate 
falls, white at first, but, as the precipitation proceeds, becoming 
gradually dirty, and at length quite brown, especially if too 
much of the nitrate be added. This precipitate, separated by 
the filter and washed, must be treated with ammonia, which dis- 
. solves the metallic salt, but leaves the sulphuret behind which 
contaminated it. The ammonia being exactly neutralised by 
weak nitric acid, the salt precipitates in a snow-white powder, 
which must be separated and dried as quickly as possible by , 
violent expression, between folds of blotting paper. This salt 
is little soluble in water, has a sweet taste, and undergoes spon- 
taneous decomposition very rapidly when kept exhaling sulphu- 
rous acid, and passing into a sulphuret, or, more probably, 
from the analogy of the hyposulphite of lead, into a sulphuretted 
oxide * *f*. 
The habitudes of this acid with the oxide of mercury are not 
less singular than its relations to that of silver. The red oxide 
of mercury is readily dissolved by a solution of hyposulphite of 
soda, while the alkali is set at liberty in a caustic state. The 
solution has a sweet but, at the same time, a mercurial taste, 
and speedily becomes turbid on standing, or on evaporation, 
even under an exhausted receiver, depositing cinnabar in abun- 
dance. The hyposulphite of mercury, then, like that of silver, 
though formed in opposition to the strongest affinities, is readily 
destroyed by the tendency of its metal to enter into a more inti- 
mate union with sulphur. 
where the principal part of his memoir is published ; and also to M. Arago’s re- 
port upon it, in tom. xi. p- .5. 
* See vol. i. pp. 8, and 396, f Sec vol. i. p. S5. 
