GLEANINGS IN SCIENCE. 
15 
sulphate, .50 of lime water, and parts of Indigo, and then boiling’ the mixture 
in water. The colour of the solution is yellow. 
Indigo thus deprived of its oxgven has been called Indigogene by Liebig : — Ber- 
zelius calls it “ reduced Indigo.” It is said to he obtained with facility in preci- 
pitation from the dyer's solution by muriatic or acetic acid, to which a small ad- 
dition of sulphite of ammonia must be made, to prevent the access of oxygen. 
Liebig asserts that this Indigogene, at a moderate temperature, absorbs oxygen 
suddenly from the air with a species of combustion, aud that in the mercurial eu- 
diometer the absorption is found to amount to lit per cent, of its weight. The 
colour changes simultaneously from white to a rich purple. 
Indigogene is soluble in the c lustio alkalies and lime water, in which it may be 
kept without alteration for any period, provided air be entirely excluded. The so- 
lution in potash forms an excellent eudiometrical liquid, as it absorbs the oxygen 
of the air with great avidity, without giving out any gas to complicate the result. 
I had occasion to remark this circumstance in the course of the experiments here- 
after described ; and as the solution may be prepared direct from the manufacturer’s 
vats in any quantity, it may prove a valuable discovery in the laboratory as a useful 
substitute for Sir Humphrey Davy's eudiometrical liquid, composed of green sul- 
phate of iron saturated with nitrous gas, which is difficult to preserve, and may 
give out a little nitrogen in its operation. It remains, however, to ascertain how 
long the alkaline solution of Indigogene will keep unaltered. 
Having thus briefly enumerated some of the principal properties of Indigo, as a 
substance sui generis, (and there appears to be no other vegetable product which re- 
sembles it in containing so much oxygen without being acid, and in the absence of 
hydrogen, and the presence of azote > 1 shall proceed to the experiments on the 
process of manufacture which form the immediate subject of this paper. 
Manufacture. 
66 The plant, after being cut and carried to the factory, is throwninto the steeper 
or superior vat, where it is pressed with timbers adapted to the walls of the vat, to 
prevent its rising in the water, which is then filled in from a reservoir, so as com- 
pletely to cover the plant.” 
During the fermentation which follows, bubble* of gas rise to the surface, to as- 
certain the nature of which our first m ention was directed. 
The bubbles collected from the vats were found to contain merely 7 or 8 percent, 
of carbonic acid; the remainder being common air, with from 12 to 18, instead of 
21, per cent, of oxygen. — Earthen vessels were inverted, and left with their mouth 
immersed all night in the vats ; hut the air in them Was found unchanged. When 
bottles were partially filled with the liquor of the vat, and well closed, the air, after 
a day, was always found in them contaminated with about 18 per cent, of carbonic 
acid, — the rest being common air, without, diminution of oxygen, excepting that 
portion due to the original air now replaced by the carbonic acid gas. 
By way of examining in a more unexceptionable manner, the gas given out 
during fermentation, the operation was conducted on a small scale, by steeping 
some of the leaves in a glass cylindric vessel furnished with stopcocks and tubes to 
convey the gas, which should lie emitted, into a glm receiver. 
After 24 hours, (for the process of fermentation does not proceed so rapidly as 
m a large vat,) the quantity of air given out by 12 sicca weight (=2160 grs-) of 
leaves, was 26.1 cubic inches : the disengagement still went on, but very slowly. 
The gas was analyzed at two different periods : towards the middle of the disen- 
gagement it was found to be composed of 
Carbonic Acid, 27-5 
Oxygen, 5.8 
Azote, 66.7 
100 
And at .the conclusion, it contained : 
Carbonic Acid, 40.5 
Oxygen, 4.5 
Azote, . — 55.0 
