A FACTITIOUS SALTPETRE, AND A MODE BY WHICH FACTITIOUS SALTPETRE MAY BE OBTAINED FOR COMMERCIAL PURPOSES
Year: 1850

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, BENJAMIN
ROTCH, of Lowlands, in the County of Middlesex, Esquire, send grecting.
WHEREAS Her present most Gracious Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twenty-second day of August, One thousand eight hundred
and fifty, did, for Herself, Her heirs and successors, give and grant unto me,
the said Benjamin Rotch, Her especial license, that I, the said Benjamin
Rotch, my exors, adññors, and assigns, or such others as I, the said Benjamin
Rotch, my exors, admors, or assigns, should at any time agree with, and no
others, from time to time and at all times during the term of fourteen years
therein expressed, should and lawfully might make, use, exercise, and vend,
within that part of Her said Majesty's United Kingdom of Great Britain and
Ireland called England, Her Dominion of Wales, and Town of Berwick-upon-
Tweed, and in Her Islands of Jersey, Guernsey, Alderney, Sark, and Man,
and also in all Her said Majesty's Colonies and Plantations abroad, the
following new Invention, communicated to me by a foreigner residing abroad,
namely, "A FACTITIOUS SALTPETRE, AND A MODE BY WHICH FACTITIOUS SALTPETRE
MAY BE OBTAINED FOR COMMERCIAL PURPOSES;" in which said Letters Patent is
contained a proviso, obliging me, the said Benjamin Rotch, by an instrument
in writing under my hand and seal, particularly to describe and ascertain the
nature of the said Invention, and in what manner the same is to be performed,
and to cause the same to be enrolled in Her said Majesty's High Court of

page_text: Chancery within six calendar months next and immediately after the date of
the said in part herein-before recited Letters Patent, as in and by the same,
reference being thereto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Benjamin Rotch, do hereby declare the nature of the said Invention to consist,
first, in a factitious saltpetre, suitable for commercial purposes, and obtained by
the conversion of nitrate of soda into nitrate of potash (or saltpetre) by the
agency of causticity, whether derived from materials in themselves caustic or
rendered caustic by the action of lime. Second, in various processes by which
the said conversion of the said nitrate of soda into the said nitrate of potash is
effected, and also by which the conversion of carbonate of potash into carbonate
of soda is effected at the same time; both these conversions being the result
of the same operations, causing the separation of the crystals of each from the
other. Thirdly, in the facilitating of the separation of the crystals of nitrate
of potash from the crystals of carbonate of soda by the agency of lime.
Fourthly, in the application of the alkali obtained from the ashes of burned
tobacco to the manufacture of factitious saltpetre; and, lastly, in the appli-
cation of ordinary centrifugal machines to the washing and drying of the
crystals of salt petre and carbonate of soda aforesaid when taken from the
mother waters.
And in further compliance with the said proviso I, the said Benjamin Rotch,
do hereby describe the manner in which the said Invention is to be performed,
by the following statement thereof, and of the various processes by which it is
effected, or which are conducing thereto, that is to say:-
And first, of the manufacture of the said factitious saltpetre, by means of
nitrate of soda and crude carbonate of potash, where the required causticity
obtained by the addition of lime; I take a quantity of the crude carbo-
nate of potash of commerce, and having reduced it to a coarse powder by
crushing or grinding, I lixiviate it with water, which I evaporate by heat
in any suitable round-bottomed iron boiler, until it obtains a density of from
40 to 45 degrees of Beaume's aerometer, when I withdraw the heat and leave
the solution a short time to settle, and when clear I draw it off and allow it
to cool, during which process of cooling, any undecomposed sulphate of potash
will separate itself, and should be removed. I let the liquid so drawn off and
The clear liquid
cooled, remain entirely undisturbed for five or six days.
should then be heated to a temperature of about 175° of Fahrenheit, and
diluted with water, until it marks fifteen degrees on Beaumè's, aerometer,
when common burnt or caustic lime should be added in the proportion of
about twenty-five per cent. of lime to the original quantity of powdered crude

page_text: carbonate of potash, and the mixture well stirred until the solution becomes
caustic, when I allow the carbonate of lime to settle and draw off the super-
natant liquor, which I then concentrate by heat and evaporation until it marks
25 degrees of Beaume's aerometer, by which process I obtain the required
caustic potash for the manufacture of the said factitious saltpetre.
Having obtained this caustic potash in a liquid state, the next process is to
mix it with nitrate of soda in such manner as to produce nitrate of potash, or,
as it is commonly called, saltpetre, and this is effected as follows:-
I
I
At the same time that the last-described operation is going on, prepare
another similar iron boiler with eight hundred quarts of hot water, into which
put two thousand pounds weight of nitrate of soda of commerce, stirring it
all the time, and adding by degrees two hundred more quarts of boiling water.
This mass also must then be raised to from 176° to 212° of Fahrenheit, and
kept at that heat for three hours, when the fire may be drawn and this mass
left undisturbed for twelve hours to settle and cool down. At the end of the
twelve hours the clear supernatant liquor which will now be found in each
of the two boilers should be simultaneously drawn off into a third shallow
iron vessel, which I call a crystalizing pan, whereupon the united liquors
being first heated to the boiling point, and then allowed very gradually and
slowly to cool down to from 54° to 50° Fahrenheit, the double conversion
already alluded to takes place, and the principal portion of the nitrate of
potash or saltpetre crystallizes out of the mother water, which should then be
drawn off into any convenient vessel, and the crystals of saltpetre collected and
thrown into an ordinary centrifugal drying machine, where they should be washed
clean with the weak mother waters, and dried by the rotatory action of the
drying machine, when they may be removed and headed up in casks, and will
be thus fit for use at any time when wanted, as saltpetre of commerce, being
as pure as Bengal saltpetre, after it has undergone the expensive process of.
refining. (Note.) The best mode of ascertaining the proportions which one
liquor should bear to the other when run together as aforesaid, is by analyzing
the liquor, and thus ascertaining the quantity of pure caustic alkali in the one.
and the quantity of pure nitrate in the other, and then providing that the
quantities run together shall contain 86 parts of pure nitrate to every forty-
eight parts of pure caustic alkali.
And now, secondly, of the process of manufacturing the said factitious salt-
petre for commercial purposes by means of nitrate of soda and American
potashes, which last-named material is usually sufficiently caustic in itself, or,.
in other words, possesses such a degree of causticity as not to require any.
addition of lime, as herein-before described; but if this should not be the case

page_text: then recourse must be had to lime, as before mentioned, inasmuch as causticity
is one of the great principles of the Invention, and if not found to a sufficient
extent in the crude materials used must be increased by the use of lime.
In order to conduct this process, I put, say, two thousand pounds of crude
nitrate of soda, as imported, into one of the iron boilers before mentioned, into
which boiler I previously place about one thousand quarts of boiling water,
and I keep up this boiling heat for about three hours, or until the nitrate of
soda is entirely dissolved and the liquor concentrated to about from 42° to 45°
of Beaumè's aerometric scale, when I draw the fire and allow the solution to
remain undisturbed for twelve hours to settle. At the same time that I am
thus dealing with the nitrate of soda, I put into the other circular iron boiler
aforesaid one thousand two hundred quarts of tepid water, and throw into this
water one thousand three hundred pounds of American potashes (the sort
usually known in the market as red American pots I prefer). This will be
ensily brought, with only a small fire, to the boiling point, and will melt and be
brought, in less than three hours, to the density required, say from 40° to 42°
of Beaumè's aerometric scale, when the fire may be drawn, and this solution
also be left undisturbed for twelve hours to settle; when the two settlements
aforesaid have taken place the two clear supernatant liquors should be heated
to from 100° to 112° of Fahrenheit, and drawn off at the same time into one
of those shallow third vessels, which I have called a crystalizing pan, and here
heated to about 112° Fahrenheit, and never allowed to fall below 80° of
Fahrenheit, at which point the crystals form, and are always larger as the heat
is more gradually diminished. This first load of crystals being formed, the
mother water should be drawn off, and the crystals remaining in the pan, which
should yield at this first operation from seven hundred to nine hundred pounds,
will be of the purest saltpetre. When they are removed from the crystalizing
pan they should be thrown at once into an ordinary centrifugal drying machine,
there washed clean with weak mother waters to get rid of all the soda that
may be adhering to them, and dried, when they will be fit for use as merchant-
able saltpetre.
Now, of course, there still remains in the mother waters, so drawn off as
aforesaid in both the herein-before described operations, a small portion of salt-
petre and a considerable quantity of carbonate of soda, though invisible from
being in a state of solution; the whole of the mother waters drawn from time
to time from the crystalizing pans must therefore be collected and returned to
one of the iron boilers aforesaid to separate the crystals of these two borlies
from each other, and there boiled down to a density of about 45° of Beaumè's
aerometric scale. At this period of the process a thin skuin will be observed

page_text: spreading itself over the surface of the liquor; this indicates that the fire
should be withdrawn, and the whole left once more quictly for twelve hours as
before, during which time the crystals of carbonate of soda settle to the bottom
of the boiler, when the supernatant liquor should be drawn off as before into
the crystalizing pan, where more crystals of saltpetre will form, and may be
collected, washed, and dried, as in the first operation.
These operations should, in fact, be repeated until all the crystals of nitrate
of potash or saltpetre, and carbonate of soda crystalize out, and are separated
and collected, washed and dried, and thus rendered fit for packing in casks or
bags for commercial purposes. In all the processes for converting the nitrate
of soda into nitrate of potash, whenever I find the principle of causticity (which
is of the essence of the Invention) wanting or not sufficiently strong in any of
the materials themselves which are used, I add lime, and by this means I am
enabled to avail myself even of the best pearlashes, and the alkali obtained
from the ashes of burned tobacco I find particularly well suited to the purposes
of the said Invention. It is evident that many improvements in the economy
of working these processes inay be discovered by a more extended practice
than has yet been devoted to carrying them out; different temperatures will
of course produce different effects, and different proportions may bring with
them various economical results, and other important advantages may yet be
taken of the various phenomena involved in the new processes for making
factitious saltpetre.
But now having described the nature of the said Invention, and the manner
in which the same is be performed, I hereby claim,
First, factitious saltpetre manufactured as aforesaid by the double con-
version of nitrate of soda into nitrate of potash, and of carbonate of potash
into carbonate of soda, by the agency of causticity.
Secondly, the process hercin-before described of manufacturing the same
from crude carbonate of potash (rendered caustic by the addition of lime) and
nitrate of soda, as herein-before described.
Thirdly, the process herein-before described of manufacturing the same from
American potashes and nitrate of soda, as herein-before described, without any
addition of lime.
Fourthly, the manufacture of carbonate of soda and caustic soda in the
process of manufacturing the said factitious saltpetre, as aforesaid, by the
double conversion of nitrate of soda into nitrate of potash, and of carbonate of
potash into carbonate of soda and caustic soda.
Fifthly, the application of the alkali obtained from the ashes of burnt
tobacco in the manufacture of the said factitious saltpetre.

page_text: And, lastly, the application of ordinary centrifugal drying machines to the
manufacture of saltpetre.
And such the Invention being to the best of my knowledge and belief
entirely new, and never before used in that part of Her said Majesty's
United Kingdom of Great Britain and Ireland called England, Her Do-
minion of Wales, or Town of Berwick-upon-Tweed, nor in any of Her said
Majesty's Islands of Guernsey, Jersey, Alderney, Sark, or Man, nor in any
of Her said Majesty's Colonics or Plantations abroad, I do hereby declare
this to be my Specification of the same, and that I do verily believe this my
said Specification doth comply fully and without reserve or disguise with the
proviso in the said herein-before in part recited Letters Patent contained;
wherefore I do hereby claim to maintain exclusive right and privilege to the
said Invention.