11 
Mr Herschel on the Hyposulphurous Acid, 
this precipitation, which, in the case of silver, are very curious, 
will be detailed hereafter. Nitrate of bismuth, when heated 
(but not otherwise) undergoes the same change ; while solutions 
of manganese, iron, zinc, copper, tin, suffer no such precipitation. 
One of the most singular characters of the hyposulphites, is 
the property their solutions possess of dissolving muriate of silver, 
and retaining it in considerable quantity in permanent solution. 
I shall now proceed to describe the salts I have succeeded in 
forming, beginning with that of lime, as being the most readily 
obtained in a state of perfect purity, and therefore best adapted to 
afford a knowledge, by its analysis, of the composition of its acid. 
Hyposulphite of lime may be formed by exposing the hydro- 
guretted sulphuret of that alkali in a flat vessel for ten or twelve 
days to the air, and in this manner it was also obtained in an 
experiment described by Dr Thomson. As this mode of proceed- 
ing is, however, very tedious and inconvenient, I soon began to 
look out for more expeditious, as well as more productive processes. 
When sulphite of lime is boiled with sulphur in a large quan- 
tity of water for a considerable time, the hyposulphite is formed, 
but usually in small quantity. This process, however, suc- 
ceeds more certainly, and yields a larger product with some of 
the other bases than with lime. But, when sulphur is present- 
ed in sufficient abundance in a nascent state, to a sulphite also 
nascent, the circumstances would seem particularly favourable 
to the union of the sulphurous acid with an additional dose of 
sulphur ; and, on trial, I found it the readiest mode of obtain- 
ing the salt in question. But before I describe the process I 
employed for this purpose, it will be necessary to say a few 
words on the combination of sulphur with lime. 
If three parts of slaked lime, and one part sulphur, be boiled 
for an hour with twenty parts water, and the liquid decanted 
while yet hot from the undissolved portion, into bottles exactly 
full and stopped, a few delicate bundles of orange-coloured 
crystals, of a plumose or acicular form, are deposited after some 
days standing ; and on emptying the bottles into a flat vessel, 
a small quantity more forms immediately. If, on the other 
hand, the solution be allowed to cool, and remain for some 
hours in contact with the sediment, a very copious formation 
of them takes place throughout its whole substance, bristling 
