Improved Washing Tank, applicable for Photographic Purposes.
Year: 1895

page_text: Date of Application, 11th Oct., 1895-Accepted, 16th Nov., 1895
Improved Washing Tank, applicable for Photographic Purposes.
I, DAVID ALLAN, of 157, Whitfield Street, London in the County of London,
Manufacturer of Photographic Requisites, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :--
The object of the present application for Letters Patent is an improved washing
tank suitable for removing solutions of chemicals from surfaces to which they
are adherent or for dissolving out small quantities of soluble substances of any
kind from the bodies in which they may be absorbed or to which they are
adherent.
The apparatus is especially designed to meet the requirements of photographic
operators it being a matter of common experience that the washing tanks at present
commonly employed by them leave much to be desired in efficiency especially under
circum-tances wherein a constant supply of water in unlimited quantities is not
obtainable, and it is therefore desirable to secure the maximum efficiency without
an undue waste of liquid. The principle on which I base my present invention is
that of the gravitation of liquids whereby a heavier substance such for instance as
a solution of a salt or similar substance tends to fall when immersed in pure water
and to accumulate at the bottom of the receptacle rather than to diffuse equally
throughout the body of liquid, in spite of the tendency of liquids to diffusion
throughout the medium in which they are immersed. I have discovered that a
considerable increase in emciency Iconite
dtc from conducting the washing operation in
the manner hereinafter described.
The washing tank which forms the object of my application for Letters Patent
may be made of any suitable shape and constructed of metal suitably protected or
in combination with other suitable material the form being any convenient one and
the material such as is not injurious to the articles to be operated upon or liable to
be acted upon by the solutions which it is intended to contain. The tank is
arranged to hold a ruck constructed of wood, metal, glass, porcelain or other
substance unattacked by the chemicals employed and provided with grooves or
otherwise. This rack is supported within the tank as may be most convenient for
the operator either by means of feet attached to it underneath or by projections or
supports secured to or forming one piece with the sides of the tank, or it may be
hung from the edges of the tank by suitable crooks or supports. I prefer to place
this rack at about one-third of the distance from the bottom to the top of the tank,
and the minimum depth of water below the rack should equal the depth of the plates
therein. At the bottom of the tank is provided an outlet for the waste washing water
or other liquid which is supplied as required from above. By this means the fresh
water passes downwards over the surfaces to be washed which in the case of
photographic plates for instance are placed in the rack in such manner that the
washing water passes between them and carries down the solutions of chemicals
dissolved out, which solutions tend to accumulate in the lower part of the tank
beneath the photographic plates or other articles to be washed.
By means of this improved tank I avoid the drawbacks incident to the usual
pattern in which the washing water soon becomes uniformly contaminated by the
solutions dissolved or washed from the plates or other objects treated, and cannot
therefore efficiently continue the purifying process.
In order to make my invention more clear I have designed by way of
illustration the apparatus illustrated in the accompanying drawing in which,

page_text: A indicates the tank, B the water inlet, the outlet, D the rack or plate holder
provided with grooves for the accommodation of the photographic plates or other
articles and shown supported by projections E forming a part of the walls of the
outer tank.
The apparatus may obviously be varied in shape or size according to the
purposes for which it is designed and may be provided with two or more inlets
and outlets, it may also possess a diaphragm or perforated plate forming the bottom
of the plate rack and to some extent preventing the retarding of the operation by
diffusion.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
The improved washing tank for photographic and other purposes having a
reservoir or container below the level of the rack for the plates or other articles
to be washed substantially as and for the purposes described in the foregoing
Specification.
Dated the 11th dure of the 1907
W. P. THOMPSON & Co.,
31 High Holborn, W.C., Patent Agents.