SECT. III.
_Apparatus necessary in Experiments upon Vinous and Putrefactive
Fermentations._
For these operations a peculiar apparatus, especially intended for this
kind of experiment, is requisite. The one I am about to describe is
finally adopted, as the best calculated for the purpose, after numerous
corrections and improvements. It consists of a large matrass, A, Pl. X.
fig. 1. holding about twelve pints, with a cap of brass a b, strongly
cemented to its mouth, and into which is screwed a bent tube c d,
furnished with a stop-cock e. To this tube is joined the glass
recipient B, having three openings, one of which communicates with the
bottle C, placed below it. To the posterior opening of this recipient is
fitted a glass tube g h i, cemented at g and i to collets of
brass, and intended to contain a very deliquescent concrete neutral
salt, such as nitrat or muriat of lime, acetite of potash, &c. This tube
communicates with two bottles D and E, filled to x and y with a
solution of caustic potash.
All the parts of this machine are joined together by accurate screws,
and the touching parts have greased leather interposed, to prevent any
passage of air. Each piece is likewise furnished with two stop-cocks, by
which its two extremities may be closed, so that we can weigh each
separately at any period of the operation.
The fermentable matter, such as sugar, with a proper quantity of yeast,
and diluted with water, is put into the matrass. Sometimes, when the
fermentation is too rapid, a considerable quantity of froth is produced,
which not only fills the neck of the matrass, but passes into the
recipient, and from thence runs down into the bottle C. On purpose to
collect this scum and must, and to prevent it from reaching the tube
filled with deliquescent salts, the recipient and connected bottle are
made of considerable capacity.
In the vinous fermentation, only carbonic acid gas is disengaged,
carrying with it a small proportion of water in solution. A great part
of this water is deposited in passing through the tube g h i, which is
262