24 Mr Herschel on the Hyposul'phurous Acid. 
The hyposulphite of copper may, however, be formed by 
digesting hyposulphite of lime on carbonate of copper, or by 
mixing sulphate of copper with hyposulphites of lime, potash, 
&e. not, indeed, in a state of purity, but sufficiently so to ascer^ 
tain its more obvious properties. It is colourless, of an intense- 
ly sweet taste, followed by a mawkish sweetness like liquorice 
root, but with no metallic flavour. It is not decomposed by 
ammonia, nor turned blue by an excess of that alkali, provided 
the air be carefully excluded, though a minute or two’s exposure 
gives it that colour. The copper in this salt is therefore in the 
state of protoxide. 
Hyposidphite qf Zinc. — portion of this salt, mixed mth 
sulphate, is formed when metallic zinc is acted on by sulphurous 
acid. The solution precipitates silver in the metallic state, but 
mercury in that of a sulphuret. 
Hyposulphite of Manganese — ^remains iii solution when that 
of lime is precipitated by sulphate of manganese. 
Hyposulphite of Tin. — Muriate of tin occasions no precipitate 
in the solution of an alkaline hyposulphite. When a piece of clean 
tinfoil is kept some days in sulphurous acidj it becomes brown 
and semitransparent, while the liquid almost coagulates with the 
quantity of oxide deposited. If now examined, however, it ex- 
hibits but faint traces of the hyposulphurous acid. 
Hyposulphite of Lead. — When a solution of nitrate of lead is 
gradually added to a neutral hyposulphite, a white precipitate 
falls, whose first portions are re-dissolved by agitation, forming, 
probably, a double salt with that in solution ; for the hyposul- 
phite of lead is very sparingly soluble, requiring not less than 
3266 parts of water to prevent its precipitation. When hypo- 
sulphite of ammonia is used and precipitated at a raised tempera- 
turej this re-dissolution takes place to a pretty considerable ex- 
tent. As the nitrate is added, the double salt is, however, at 
last decomposed again, and nearly the whole acid falls in com- 
bination with litharge. This precipitate is a white mealy pow- 
der, which, held long in the mouth, leaves an impression of 
sweetness. When heated, even below 212° F. it turns black; 
and, when the heat is raised, takes fire, becoming red hot, and 
Hirns with a weak flame. If now removed from the fire, the 
