By this formula I have no difficulties whatever; my plates set in about
five minutes, and their quality is such that, "unless a better method is
devised," I intend to adopt it in all weathers.
One word more as to the alcohol. It will prevent the decomposition of
gelatine when boiling goes on, or when in the presence of foreign salts;
no flocculent deposit is noticed in the alcohol after the emulsion has
been precipitated.--_Photographic News_.
* * * * *
THE DISTILLATION AND RECTIFICATION OF ALCOHOLS BY THE RATIONAL USE OF
LOW TEMPERATURES.
By RAOUL PICTET.
The industrial problem of the rectification of alcohols is based
entirely upon the properties of volatile liquids, upon the laws of the
maximum tensions of the vapors of these liquids, and upon the influence
of temperature upon those different elements which find themselves in
presence of each other in an alembic.
If we desire to follow, in their least details, all the phenomena which
succeed one another in a rectifying column, and which are connected with
one another by a continuous chain of reciprocal influences, the problem
becomes exceedingly complex.
[Illustration: PICTET'S APPARATUS FOR THE RECTIFICATION OF ALCOHOL BY
COLD.]
In order that the new applications of the mechanical theory of heat may
be readily understood, we shall divide this problem into a series of
propositions, which we shall examine separately, and which collectively
constitutes in its general features the methodical rectification of
liquids.
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