ge 
Miscellanies. 195 
is that of agitation for some time in water, in a well corked bottle; 
but, he observes, the powder obtained by this method is very imper- 
fect; whereas if alcohol at 36° be used instead of water, a powder of 
the utmost fineness is produced, which has a crystalline appearance, 
and on agitating the liquid in the sun, the botile appears to be entirely 
filled with a light brilliant powder.—Idem. 
21.. Preparation of Sugar from Starch.—M. Heinrich says, that 
from one to two parts of sulphuric acid for each 100 parts of potato 
starch is sufficient, if the heat applied be a few degrees above 212 
- Pahr.; and also, that then two or three hours are sufficient to give 
erystallizable sugar. He applies the heat in wooden vessels by mea 
_ of steam.—(Roy. Institution Jour. June, 1830.)—Jdem. 
22. Sulphate of Potash and Copper.—When equal quantities of | 
Sulphate of potash and sulphate of copper are mixed, a particularly 
bright, green precipitate is gradually formed, which Vogel considered 
asa subsalt. Having been analysed by Brunner, it appears to con- 
sist of 
Oxide of Copper, — - - . - - - 39.23 
Potash, PEE ROSE T Ree  aereme - S 
Sulphuric acid, : - - - - - 39.70 
Water, eR A ee are Se ee eee 
100.00 
Idem. 
23. On improvement in black writing ink ; by John Bostoch, M. D. 
FR.S., é&¢.—(Transactions of the Society of Arts of London.)— 
The changes, which tend the most to impair the value of ink, are its 
Moulding, the separation of the black matter from the fluid, and its 
foss of color,—the black first changing to brown, and at length disap- 
‘Pearing. The author considers the gallic acid to be the only part of 
‘the solution of the gall nut, which is essentially concerned in the pro- 
- duction of permanent black ink, and that the tan, the mucilage, and 
the extractive matter are the causes of its deterioration. The mould- 
ing is considered as arising from the mucilage, and the precipitation 
to be chiefly occasioned by the extractive matter. The tan, it is con- 
jectured, forms a triple compound, in the first instance, with gallic 
acid and the iron; and that in consequence of the decomposition of 
the tan, this compound is afterwards destroyed. 
The practical conclusions, says the author, that I think myself war- 
‘anted in drawing from these experiments, are as follows :—In order 
‘© procure an ink, which may be litile disposed either to mould or 
