IMPROVEMENTS IN THE CONSTRUCTION OF FILTERS AND IN THE PROVISIONAL SPECIFICATIONTIONS AND IN THE PREPARATION OF MATERIALS USED FOR THE PURIFICATION OF WATER
Year: 1874

page_text: LETTERS. PATENT to Gustav Bischof, of the Andersonian University,
in the City of Glasgow, Professor of Technical Chemistry, for the
Invention of "IMPROVEMENTS IN THE CONSTRUCTION OF FILTERS AND IN THE
PROVISIONAL SPECIFICATION left by the said Gustav Bischof
at the Office of the Commissioners of Patents, with his Petition,
on the 29th June 1874.*
I, GUSTAV BISCHOF, of the Andersonian University, in the City of
5 Glasgow, Professor of Technical Chemistry, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN THE CONSTRUCTION OF
FILTERS AND IN THE PREPARATION OF MATERIALS USED FOR THE PURIFICATION OF
WATER," to be as follows:―
This Invention relates to improvements in the construction of
? filters and in the preparation of materials used for the purification of
water.
In filters as usually constructed the filtering materials, such as char-
coal, sand, or similar substances, rest upon a perforated bottom, below

page_text: which is a receptacle for receiving the filtered water. When a quantity
of water is withdrawn from this receptacle a farther supply of the
unfiltered water is usually caused to flow with considerable rapidity
through the filtering materials unless they are packed very tight. Thus
the water is either liable to be imperfectly purified and to become muddy
owing to its rapid transit through the filtering materials, or the latter are
liable to be choked if packed very tight. One of my improvements
relates to means of remedying this defect. Below the perforated bottom
I place a second bottom without perforations, but preferably made
shelving towards the middle, from which a bent pipe is led to the
exterior of the filter. In the side of this pipe I bore a small hole which
forms the only communication between the upper part of the filter and
the receptacle for filtered water. The size of the hole is so regulated as
to retard the passage of water through the filtering materials so that the
latter cannot be disturbed, and that the water may bo thoroughly
purified by sufficient contact with the filtering materials. In ordinary
working the end of this bent pipe outside the filter is closed by a cock
or plug, and the purified water then flows through the small hole in the
side of the pipe into the receptacle for filtered water.
When it is desired to cleanse the filter the cock is opened or the plug
is withdrawn and water then flows out by the bent pipe without
mingling with the filtered water in the receptacle, but rather tending to
draw water or air therefrom through the small hole in the side of the
pipe, and so clearing it of any obstruction.
Another of my improvements relates to the use of hydrated ferric
oxide for purifying water. This substance may be conveniently applied
for this purpose by mixing it with the materials used in forming slabs or
hollow balls of porous material, such as are often employed for filtering
purposes. Or such porous slabs or balls may be impregnated with the
hydrated ferric oxide in the following manner :-They are first soaked in
a solution of a salt of iron, such as the ferric or ferrous chloride or
sulphate, and then soaked in a solution of an alkaline oxide or carbonate
which has the effect of precipitating the hydrated ferrous or ferric oxide
within the pores of the slabs or balls. The hydrated ferrous oxide which
is precipitated, if a ferrous salt has been employed, is converted into
hydrated ferric oxide by exposure to the atmosphere.

page_text: ·SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Gustav Bischof in the Great Seal Patent Office
on the 24th December 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GUSTAV
BISCHOF, of the Andersonian University; in the City of Glasgow,
Professor of Technical Chemistry, send greeting..
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-ninth day of June, in the year
of our Lord One thousand eight hundred and seventy-four, in the thirty-
cighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Gustav Bischof, Her special license
that I, the said Gustav Bischof, my executors, administrators, and
assigns, or such others as I, the said Gustav Bischof, my executors,
administrators, and assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for
$6 IMPROVEMENTS IN
THE CONSTRUCTION OF FILTERS AND IN THE PREPARATION OF MATERIALS USED
FOR THE PURIFICATION OF WATER," upon the condition (amongst others)
that I, the said Gustav Bischof, my exccutors or administrators, by
an instrument in writing under my, or their, or one of their hands and
seals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Scal Patent Office within
six calendar months next and immediately after the date of the said
Letters Patent.
-
NOW KNOW YE, that I, the said Gustav Bischof, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement thereof, reference being had to the accompanying
Drawing and to the letters marked thereon, that is to say
This Invention relates to improvements in the construction of
filters and in the preparation of materials used for the purification of
water.

page_text: In filters as they are usually constructed the filtering materials, such
as charcoal, sand, or similar substances, rest upon a perforated bottom,
The
below which is a receptacle for receiving the filtered water.
efficiency of the filter depends in a great measure upon the time during
which the water is exposed to the action of the purifying materials. If,
on the one hand the yield be too large, the purification of the water is
imperfect from the want of sufficiently long exposure to the-purifying
action, and moreover the water is apt to become turbid, carrying with it
fine particles of the filtering material, and this is particularly the case
when a quantity of water is withdrawn from the receptacle, whereupon
a farther supply is usually caused to flow with considerable rapidity
through the filtering materials unless they are very tightly packed. If
on the other hand, by tight packing of the materials or otherwise the
yield be reduced too much, the utility of the apparatus is diminished,
and the filter, moreover, is apt to become choked. The regulation of
the yield in filters has hitherto been attempted by compressing more or
less the filtering materials, or by passing the water through compressed
fibrous substances, such as asbestos. But in filters so regulated, after a
time the interstices become charged with impurities deposited from the
water, and the yield becomes very much reduced or entirely arrested.
In order to provide for a proper regulation of the flow through filters
without introducing the defects which I have mentioned above, I apply
to filters a regulator which I will describe, referring to the accompanying
Drawing which represents a part vertical section through a filter,
shewing the lower portion of the filtering vessel and the receptacle
beneath it. The filtering materials which are not represented in the
diagram rest upon a perforated bottom a, beneath which I provide a
solid bottom b, b, having a trough-shaped cavity or pocket 61 in its
middle. Below this bottom is the receptacle for filtered water c, from
which the water is withdrawn from time to time by a cock c³. Through
the side of the receptacle c and of the pocket 6' I pass a pipe d, securing
it by cement or otherwise in a water-tight manner. The inner end of
this pipe is somewhat contracted as shewn at d, its outer end e is fitted
with a plug or provided with a stop cock. At some part of the pipe d,
within the receptacle c, and preferably on the upper side of the pipe, I
make a small hole n of a sized adjusted to the desired yield of the filter,
that is to say, of such an area that under the pressure of the column of
water in the filter, allowing for retardation by friction the quantity of

page_text: เ
water passing through the filter and through the hole n in a given time
shall be that which is most suitable for perfect purification. Besides the
passage by the hole n there is no other communication between the
filter and the receptacle c. In ordinary working of the filter the end e
of the pipe is closed by a plug or by the stop cock, and as water is with.
drawn from the receptacle c a fresh supply passes slowly through the
filter and the hole n, the rapidity of the flow never exceeding that which
is suited to complete purification. As the hole n is small, particularly
in domestic filters, it may become choked, in which case the pipe d may
be opened at the end so as to allow water to flow freely out and clear
out matter that may have become deposited in the pipe. A brush may
be also introduced to clear the inner orifice of the hole n.
is thus allowed to flow through d owing to the contraction of its inner
end the stream does not entirely fill the pipe but creates a certain
indraught at n which has the effect of thoroughly clearing the hole.
When water
It may be readily understood that in the case of large filters several
pipes, such as d, may be provided and arranged as may be found most
convenient to give access to them for cleansing.
When a filter is provided with a regulating apparatus such as I have
described the filtering materials may be charged in a comparatively loose
condition with much less risk of becoming choked than when they aro
compressed, and while the filter requires little or no attention the yield
continues regular, and does not materially vary, even when on recharging
the filter the looseness or compactness of the filtering materials may be
considerably altered. The opening of the pipe d from time to time,
besides clearing the pipe itself, has the effect of washing the filtering
materials by permitting the flow through them of a much larger volume
'The water so
of water than can in ordinary working pass the hole n.
passed, which may be somewhat turbid or impure, is carried outside the
receptacle without mingling with its purified contents.
In preparing materials for the purification of water according to my
present Invention I employ hydrated ferric oxide, which may either be
mixed with the materials used in forming the porous slabs or hollow
balls often employed for filtering purposes, or which may be introduced
into such slabs or balls by impregnation in the following manner :—
They are first soaked in a solution of a salt of iron, such as the ferric or
ferrous chloride or sulphate, and then soaked in a solution of an

page_text: alkaline oxide or carbonate which has the effect of precipitating hydrated
ferrous or ferric oxide within the pores of the slabs or balls. The
hydrated ferrous oxide which is precipitated when a ferrous salt has
been employed is converted into hydrated ferric oxide by exposure to
the atmosphere.
Having thus described the nature of my Invention, and in what|
manner the same is to be performed, I claim,-
First. The use for regulating the flow of water through filters of a
pipe communicating by a small outflow hole with the receptacle of
filtered water, arranged and operating substantially as herein described.
Second. The use, for the purification of water, of hydrated ferric oxide,
either mingled with the materials forming porous filtering slabs or
balls, or deposited in the pores thereof by impregnation, substantially as
lierein described.
In witness whereof, I, the said Gustav Bischof, have hercunto
set my hand and seal, this Twenty-first day of December, in
the year of our Lord One thousand eight hundred and seventy-
four.