Considerable suspicion has of late been thrown upon the thoroughness of
the alcohol method, unless the emulsion has, previous to precipitation,
been freed of the greater part of the soluble salts by washing; that is
to say, it is doubtful whether the whole of the soluble salts can be
eliminated by the process, and, therefore, unless in exceptionally hot
weather, it would seem best not to trust to it, except as a further
security against soluble bromide and nitrate after washing. Besides
this, the consumption of alcohol is very large. Almost three times the
amount of the emulsion precipitated is required, and this, even when
methylated spirit is used, adds considerably to the expense. With a view
of doing away with the washing altogether, or, rather, of washing of
the silver bromide when not incorporated with the gelatine, several
processes have been invented. By these silver bromide is obtained in a
very fine state of division, ready to mix with gelatine and water in any
proportion.

The best known of them is Captain Abney's very ingenious glycerine
method, which seems to have been thoroughly successful in his hands,
although it has not been in every one's. The silver bromide obtained by
his process is not highly sensitive, and requires boiling with gelatine
before it is in a fit state to make a rapid plate.

We have lately had described in these columns a method of obtaining
bromide in a highly-sensitive state by means of the use of an acid,
whereby, after emulsifying and boiling, the viscosity of the gelatine
was destroyed, and the bromide in time deposited itself. During the late
hot weather, when washing became almost impossible, I was led to cast
about for some method of eliminating the soluble salts less tedious and
"sloppy" than that of washing, more certain and less expensive than that