IMPROVEMENTS IN REFINING SALTPETRE AND IN APPARATUS FOR THE SAME.
Year: 1874

page_text: LETTERS PATENT to George Haycraft, of Faversham, in the County
of Kent, for the Invention of "IMPROVEMENTS IN REFINING SALTPETRE
AND IN APPARATUS FOR THE SAME.'
"
Sealed the 7th May 1875, and dated the 25th November 1874.
PROVISIONAL SPECIFICATION left by the said George Haycraft at the
Office of the Commissioners of Patents, with his Petition, on the
25th November 1874.
I, GEORGE HAYCRAFT, of Faversham, in the County of Kent, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN
REFINING SALTPETRE AND IN APPARATUS FOR THE SAME," to be as follows :―
My Invention relates, 1st., to the arrangement of the several vessels
in which the successive stages of the process of refining saltpetre are
performed in such a way that the grough or unrefined saltpetre being
submitted to the first stage of the refining process, namely, the boiling
at a sufficient altitude, will be caused to pass by gravitation alone from
vessel to vessel through all the successive stages of the process until the

page_text: refining is completed, whereby hand labour and the use of pumps for
lifting the saltpetre from one level to another are dispensed with.
My Invention also relates to the method of boiling the unrefined
saltpetre by introducing steam among the mass, whereby the water
necessary for dissolving the saltpetre is procured by the condensation of 5
the steam among the mass, and its temperature is kept at or near the
boiling point during the entire operation.
My Invention also relates to the method of recovering saltpetre from
the mother liquor which drains from the refined saltpetre.
My Invention also relates to the method of cooling the saltpetre 1
during crystallization, and to other details of the process herein-after
more fully described, as well as to the construction of the boiling and
reducing vats, the agitators in the crystallizing vats, and the gearing for
driving the same.
According to my Invention the grough saltpetre is boiled in vats by 1
means of a steam coil or worm, together with. steam injected amongst
the mass of grough saltpetre where it condenses, and thus furnishes the
water necessary for dissolving the saltpetre, the temperature being also
by this means maintained at or near the boiling point during the entire
operation, which is therefore considerably accelerated, or the steam 2
injector may be used alone without the steam coil. The boiled saltpetre
is thence run off into filters disposed at a lower level, whence it flows
into crystallizing vats provided with mechanical agitators, and in order
to hasten the cooling a blast of cold air is directed upon the surface of
the saltpetre, whereby crystallization is promoted. The gearing for 2
driving the agitators is disposed beneath the crystallizing vats instead of
above, as usual, whereby the liability of foreign substances falling from
the gearing into the saltpetre is avoided. The crystallized saltpetre is
then made to gravitate into schawls or waggons provided with a filtering
surface at bottom, wherein it is washed by the water of condensation 3
from the steam coils of the boiling or reducing vats, which is collected
in vats placed at a suitable elevation above the schawls or waggons. By
this arrangement the necessity of pumping or raising water for washing
the saltpetre is avoided.
The mother liquor draining from the refined saltpetre in the filters of 3
the schawls or waggons is received in a tank below, from which it is
pumped to a suitable clevation, where it is received in a vat and

page_text: evaporated until the proper specific gravity is attained by means of a
steam coil or worm, the resulting saltpetre being then filtered and
discharged into the crystallizing vats before mentioned and treated in a
similar manner to that before described for the grough saltpetre when
boiled and filtered. In this manner the necessity of returning the
saltpetre so recovered from the mother liquid to the boiling pot to be
treated over again as grough saltpetre is dispensed with.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said George Haycraft in the Great Seal Patent Office
on the 25th May 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
HAYCRAFT, of Faversham, in the County of Kent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fifth day of November, in the
year of our Lord One thousand eight hundred and seventy-four, in the
thirty-eighth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said George Haycraft, Her special
license that I, the said George Haycraft, my executors, administrators,
and assigns, or such others as I, the said George Haycraft, 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 "IMPROVEMENTS IN
REFINING SALTPETRE AND IN APPARATUS FOR THE SAME," upon the condition
(amongst others) that I, the said George Haycraft, my executors 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 Seal Patent
Office within six calendar months next and immediately after the date
of the said Letters Patent.

page_text: condenses, and thus furnishes the water necessary for dissolving the
saltpetre, the temperature being also by this means maintained at or
near the boiling point during the entire operation, which is therefore
considerably accelerated. The steam injector C may be used either
alone without the steam coil B, or they may be used in combination.
When the boiling is complete the cocks D are opened to run off the
boiled saltpetre from vats A. into filters E of wood or copper, provided with
suitable straining cloths and disposed at a lower level, whence it flows
by spouts into crystallizing vats F provided with mechanical agitators G,
which by their motion expose fresh surfaces of the saltpetre and assist
the cooling; and in order to further hasten the cooling a blast of cold
air from a fan H is directed upon the surface of the saltpetre, whereby
crystallization is promoted. The agitators G are driven by gearing
disposed beneath the crystallizing vats F instead of above as usual,
whereby the liability of foreign substances falling from the gearing into
the saltpetre is avoided. When sufficiently cool the saltpetre is run off
through a sliding valve I into schawls or waggons K, in which the
mother liquor is allowed to drain from the crystals and run off through
a cock at bottom into the mother liquor tank L beneath. The crystals
are then washed with distilled water, which may be the water of con-
densation from the steam coils of the boiling or reducing vats, which is
collected in vats M placed at a suitable elevation above the schawls or
waggons K, by which arrangement the necessity of pumping or raising
water for washing the saltpetre is avoided. The outlet cock of the
schawl is then connected with an exhaust pump N, whereby the crystals
are freed from the water retained in the mass by capillary attraction,
which water is also discharged into the mother liquor tank, the saltpetre
in the schawl is then fit for use.
The mother liquor received in the tank L is raised by a pump at P
into reducing vats ○ where it is evaporated by means of a steam coil
to a saturated solution of saltpetre, and is then filtered at E¹ and
discharged into the crystallizing vats F, where it is agitated and cooled,
and afterwards washed and treated as before to recover the saltpetre.
In the method hitherto followed the saltpetre is allowed to crystallize
in open rectangular vats and then recovered as grough saltpetre and
treated accordingly, but by the improved method above described the
saltpetre is recovered at once from the liquor without the labour of