^ Mr Herschel an the Hypomlphurous Acid. 
strongest chemical affinities, has not, to the best of mj know- 
ledge, been noticed. It is not peculiar to the hyposulphite ; as 
the muriate, nitrate, and, I presume, any other salt of hme, 
may be substituted with the same success. When citrate of 
alumina is used, a precipitation takes place, but it is not abun- 
dant, and a portion of both the undecomposed salts remains in 
solution. Sulphate of alumina concentrated precipitates it much 
more copiously ; but here, again, some of both salts remains 
undecomposed. This latter precipitant would probably, how- 
ever, give a satisfactory result with the hyposulphite of strontia ; 
but my stock of that salt being very small, I had no opportuni- 
ty of making the trial properly. When sulphate of alumina is 
boiled 'vvith sulphur, the solution gives up nearly all its saline 
contents, but evaporated, leaves small gritty grains, of no de- 
terminate form. 
Hyposulphite of' Iron, — Berthollet, in a memoir communicated 
to the French Academy in 1789, has shown that, when iron is 
subjected to the action of sulphurous acid, the acid is decom- 
posed, and a sulphite formed ‘‘ avec lequel le soufre degage a 
assez d’affinite pour se tenir en dissolution.” The fact is, that a 
true hyposulphite is formed, precipitating nitrates of silver and 
mercury in sulphurets, &c. 
When sulphurous acid is poured on newly precipitated car- 
bonate of iron, a deep red-brown solution is slowly formed. 
When heated per se, this undergoes decomposition, but if boil- 
ed on sulphur, the whole forms hyposulphite of iron. Its taste 
is strongly ferruginous, it is nearly colourless, and precipitates 
ferro-cyanate of potash white. When concentrated by evapora- 
tion, it does not crystallize, but settles into a glutinous mass of 
a dirty white colour, not unlike glazieFs putty. This salt may 
likemse be formed by boiling hyposulphite of lime on carbonate 
of iron, a portion of the carbonate being at the same time con- 
verted into sulphuret. The theory of this svill be more obvious 
when we have become acquainted mth 
Hyposulphite of Copper. — Sulphurous acid, according to Ber- 
thoUet, has no action on metallic copper. When digested, how- 
ever, on carbonate of copper, either cold or assisted by heat, the 
carbonate being in excess, I have observed that a blue solution 
is formed with effervescence, having every character of a sid- 
