28 
l\Ir Hersciiel on ilie Myposulphurous Acid. 
HypomlpMU of Mercury . — Pure nitrate of mercury, entirely 
free from oxynitrate (the white crystals which form spontane- 
ously when nitric acid of 1.34, diluted with an equal weight of 
water, is allowed to stand on a large excess of mercury at 45® F.) 
causes an instant black precipitate in the most dilute or the 
most concentrated solution of an hyposulphite. When the 
{Solution contains a lOjOOOth of its weight of hyposulphurous 
acid, it immediately strikes a deep brown, and when only a 
100,000th is present, it opalesces on a few minutes standing. 
Hyposulphite of the protoxide of mercury, therefore, does not 
exist. Calomel is also immediately blackened by any hyposul- 
phite. 
When corrosive sublimate, dissolved in 20 times its weight of 
water, is poured in small quantity into a very dilute hyposul- 
phite of lime, the usual redissolution of the first portions of the 
precipitate takes place (though to a very small amount), and 
when added in large excess, a light-yellow muddy precipitate 
separates in abundance. 100 grains of the standard solution so 
often mentioned gave 32.27 grains of this substance, well dried, 
and the filtered liquor afterwards afforded 21.50 grains ignited 
sulphate of baryta, that is, respectively 141.2 and 94.1 per cent, 
on the crystallized salt, or 384.7 and 256.3 on the acid itself. 
These numbers (at least the latter) I can reconcile to no theory. 
The former certainly agrees in some measure with the acidifica- 
tion of one atom of sulphur, as in the case of oxynitrate of silver. 
The only probable explanation of this precipitation seems to be, 
the simultaneous formation of hyposulphite of mercury, calomel, 
and sulphuric acid, accompanied by a deposition of sulphur, 
though this will agree but ill with the numbers set down. Yet 
the experiment was made with every precaution to secure exact- 
ness. 
My trials to obtain hyposulphurous acid in a separate state, 
though not fully successful, seem not entirely to preclude a hope 
of accomplishing it. The displacement of this acid by all the 
more powerful ones is accompanied with decomposition, but 
when sulphuretted hydrogen was made to act on hyposulphite 
of lead suspended in water, though by far the greater portion of 
the acid was uniformly destroyed, I did certainly once succeed 
in procuring a liquid which, wh^m filtered, had a weak, acid, 
