Mr Herschel on the Hyposutphurous Acid, 
and 1.6S8. When a beam of polarized light is transmitted 
nearly at right angles, through a plate of this salt, bounded on 
either side by the principal natural joint, and analysed at its 
egress by a prism of Iceland spar, in the usual manner, a set of 
coloured fringes is seen, whose elliptic figure, as Dr Brewster 
has shown in his elaborate researches on this subject, indicates 
the existence of more than one polarizing axis in the crystal. 
Hyposulphite of lime is very soluble in water, that fluid, at 
57° F., being capable of dissolving nearly its own weight, during 
which the thermometer falls to 31°. The specific gravity of a 
solution, saturated at 50°, is 1.300 ; and when the specific gra- 
vity is 1.114371 at 60°, -the solution contains 0.2081 of its 
weight. Its crystals are not altered by exposure to air of the 
usual degree of moisture ; but, when dried by sulphuric acid in 
•vacuo, or at 100° F. in the air, they become covered with a 
white crust, like phosphate of soda, which destroys their lustre, 
^vithout impairing their figure. They are insoluble in alcohol 
of 0.82344, which also precipitates them in spiculae, from their 
solution in water. 
In order to attain a knowledge of the composition of this salt^ 
I made the following experiments. 
1454.75 grains of the crystallized salt, carefully dried in a 
very moderate temperature, were dissolved in distilled water. 
The weight of the solution so produced (which I shall call, for 
distinction’s sake, the standard solution), was 6365.62 grainS;^ 
so that every hundred grains contained 22.8532 of the crystals. 
600 grains of this solution, containing 137.12 of the crystals, 
were precipitated with carbonate of ammonia, adding, at the same 
time, some of the pure alkali, to absorb a slight excess of carbo- 
nic acid, which prevents the precipitate adhering to the vessels. 
Collected with extreme care and no loss, and gently ignited, the 
carbonate of lime weighed 53.01, (or 38.66 per cent., equivalent 
to 21.77 lime). 100 grains of the crystals themselves, from the 
same parcel, gave, by a similar process, 38.65 carbonate, or 
21.765 lime. 
130 grains of the same parcel of crystals, decomposed by 
heat in a small retort over a powerful Argand lamp, underwent 
a partial fusion into a white opake cream ; after which, the de- 
composition was indicated by sulphur separating and attaching 
