Is Mr Herscliel on the Ryposidphurous Acid. 
over its surface, and even hanging down from that of the liquid. 
These crystals, which I do not find described in any of the 
usual works, are easily separated, by washing, from the greater 
part of the impurities in which they are formed, though a por- 
tion adheres obstinately. They cannot be dried in contact with 
air, without immediate decomposition, but, by subjecting them 
under an exhausted receiver,^ to the absorbent power of a large 
surface of sulphuric acid, they may be obtained free from ad- 
hering moisture, after which they are permanent in a dry atmo- 
sphere. They are very sparingly soluble in cold water. By 
keeping a large excess of them in that liquid for a month, be- 
tween the temperatures and 45'’ F., with frequent agitation, 
their solution had no higher specific gravity than 1.0105 ; it 
had a wine-yellow colour, and an acrid, bitter and sulphureous 
taste. Hot water dissolves a much larger portion, which it does 
not deposit on cooling, unless lime or some other body in fine 
powder be added. Their figure, when slowly formed, (by keep- 
ing a portion of their solution formed by heat, but allowed to 
grow quite cold, on lime for a month,) is that of hexangular 
plates, with two of their sides longer than the rest ; or, which 
comes to the same, quadrilateral prisms somewhat elongated, 
and terminated by diedral summits. 
I was not able to proc’ure this substance in any quantity in 
a state of sufficient purity for exact analysis, so that the follow- 
ing must be regai’ded as only approximative, and to be correct- 
ed by the theory of definite proportions. 
43 grains, decomposed by dilute muriatic acid, gave 3S.7S 
carbonate, answering to 18.43 lime, or 42.88 per cent. Sul- 
phuretted hydrogen was developed, and a quantity of sulphur 
separated, wffiich, after fusion, weighed 5.35 grains (12.44 per 
cent.). Now, 42.88 lime, if united to sulphur in the proportion 
expressed by the formula 2L -f S, would require 12.08 of that 
substance. 
* This beautiful discovei'y of Mr Leslie, promises to be of extreme utilit}i in 
experimental chemistry. I have had occasion to experience its efficacy, in esti- 
mating the total saline contents of mineral waters by evaporating them in a frozen 
state, and ha^ e satisfied myself, by comparative experiments, that no portion of 
the solid matter is lost — an inestimable advantage, which enables us to operate ob 
a few ounces with as much exactness as on as many quarts in the usual way. 
