58 
ON POTATO SUGAR. 
the peroxide of manganinm should be used, which entirely 
prevents the evolution of sulphurous acid during the ebulli- 
tion. The solution is now to be filtered, and evaporated to 
dryness ; after which it may be gently heated until no more 
sulphurous acid is disengaged. 
The salt thus obtained is very nearly white, possessing a 
scarcely perceptible rose tint. As I have obtained it, it has 
a slight acid re-action ; this, if required, can be rectified by 
a second solution, and the addition of a small quantity of 
carbonate of baryta. The salt contains no metal but man- 
ganium. I find the best test for a persalt of iron in a man- 
ganium salt to be the sulphocyanide of potassium. — Lond. 
Chemist. 
ART. XIV. — ON POTATO SUGAR. 
By Mr. John A. Spencer. 
Wishing a short time since to prepare a specimen of 
grape sugar from potato starch, and not feeling satisfied 
with the product obtained by the use of oil of vitriol, in 
consequence of the sulphate of lime retained in solution, it 
struck me that if I used an acid whose lime-salt was more 
insoluble than the sulphate, the product would be improved; 
I therefore used oxalic acid, and was not disappointed in 
my expectation. 
Four parts of potato starch, twenty parts of water, and 
one part of oxalic acid, dissolved in water, were boiled 
together, and in less than ten minutes the mixture, from 
being so thick, that the vessel which contained it might 
have been inverted for a few moments without risk of loss, 
became as thin and limpid as water ; the boiling was con- 
