155 
Mr Herschel on tlie Hypomlphurous Acid. 
Hyposulphite of Mercury and Potash . — On a quantity of 
orange carbonate of mercury, I poured a solution of hyposul- 
phite of lime : It blackened, aud a considerable portion dissolv- 
ed, Into this I poured an excess of carbonate of ammonia, which 
separated the very small quantity of lime still remaining in solu- 
tion, but left the oxide of mercury. Being cleared by filtration, 
carbonate of potash was poured in, when a white crystallised salt 
separated in abundance. The liquor, when moderately heated, 
grew turbid, and deposited a quantity of vermilion of the richest 
colour, after which it underwent no farther decomposition, even 
by continued ebullition, and on filtering and cooling, deposited 
abundant crystals of the same salt. This is a double hyposul- 
phite, analogous to that with silver for its base. It is much 
more soluble in hot water than cold, and crystallises, in cooling, 
in spicular tufts. By careful management, however, it may also 
be obtained in oblong rectangular tables, bevelled at all the edges, 
or, which comes to the same thing, flattened six-sided prisms, ter- 
minated by two planes set on the longer edges. These are co- 
lourless and transparent, and their optical properties, on exposure 
to polarised light, present anomalies of a very extraordinary nature, 
which may be described more properly on some other occasion. 
The action of oxide of lead on a liquid hyposulphite, is ana- 
logous to that of the oxides of silver and of mercury, but less 
strongly marked. When hyposulphite of soda was ground with 
litharge, no sensible effect was produced ; but on allowing the 
mixture to stand twenty-four hours, the litharge became caked 
together, and its surface to some depth was found converted in- 
to a white mass. The supernatant liquid had now acquired a 
very sensible causticity, and immediately turned vegetable blues 
green, &c. The decomposition, however, proceeded no farther, 
and was never complete. The brown and red oxides of lead 
produce no such effect, nor have any other of the metallic 
oxides or hydrates which I have tried any considerable action. 
I cannot forbear noticing here, though not relevant to the 
present subject, a phenomenon which occurred to me in the 
preparation of mercurial salts for some of the foregoing 
experiments. I had procured a quantity of the crystallized 
proto-nitrate, which forms when dilute nitric acid is allow- 
ed to remain in a moderately warm temperature on excess of 
