IMPROVEMENTS IN THE MANUFACTURE OR PRODUCTION OF SALTPETRE, AND THE PREPARATION OF MATERIALS FOR THE PURPOSE
Year: 1858

page_text: PROVISIONAL SPECIFICATION left by Michael Henry at the Office
of the Commissioners of Patents, with his Petition, on the 10th August
1858. A communication.
I, MICHAEL HENRY, of 84, Fleet Street, in the City of London, Patent
Agent, do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN THE MANUFACTURE OR PRODUCTION OF SALTPETRE, AND THE PREPARATION OF
MATERIALS FOR THE PURPOSE," communicated to me by a foreigner residing
abroad, to be as follows:-
The cost of imported nitrate of potassa, and the diminution of artificial
nitre beds, have led to the production of saltpetre by double decomposition,
treating nitrate of soda with carbonate of potassa extracted from vegetable
ashes, Now the present process as communicated to me is based on the
greater affinity of nitric acid for pure potassa than for soda, and on the deli-
quescence of hydrate of soda, which allows of the ready separation of such
hydrate from the nitrate of potassa by a few washings. According to my
process, nitrate of soda is treated with caustic potassa direct, instead of with a
salt of potassa, which is never free from extraneous matters. The caustic
potassa may be obtained by utilizing the property peculiar to hydro-fluosilicic
acid of precipitating potassa from its solutions. The process also embraces
the production of caustic soda. I propose to prepare potassa by causing
hydro-fluosilicic acid to act on ashes of vegetable substances, especially the
pulp and radicles of beetroot, and to prepare soda by causing hydro-fluo-
silicic acid to act on sea salt or chloride of sodium.

page_text: In performing the manufacture, the mode preferred for obtaining hydro-
fluosilicic acid, is to cause steam to act on fluor spar, combined with equal
parts of silex, in a reverberatory furnace, or in retorts (similar to those used
for zinc) or by disengaging fluoride of silicium in a gaseous state, and immersing
it in a receiver, wherein it is converted by contact with water into hydro-
fluosilicic acid. Caustic potassa I prefer to extract from ashes obtained by the
¡ncineration of the radicles and pulp of beetroot (residua of sugar manufac-
tories), precipitating it by hydro-fluosilicic acid, and treating the precipitate
with about an equal weight of recently slaked lime and about ten times its
weight of water in a covered boiler, keeping up ebullition till a small quantity
deposited or filtered ceases to be disturbed by the lime water.
The soda may be obtained by the reaction of hydro-fluosilicic acid on sea salt
or chloride of sodium, in the proportion (3s F+2 sil F³) when hydrochloric
acid and fluosilicate of soda will be formed; the latter when heated gently in
an atmosphere containing steam is decomposed into fluoride of sodium, which
may be converted into soda by means of lime (3 Na F+ 2 si F³); this mode
of producing soda allows of the application of Mr. de Lucas' process for
directly proceeding by treating these bases with ozonized air, to obtain
nitrate of soda.
The constituent materials being thus prepared, I prefer to proceed as
follows: Potash lye, obtained as described, is caused to deposit in a boiler
(closed so as not to absorb carbonic acid from the air), and is thence drawn off
into a second covered boiler, and brought into the presence of a clear
solution of nitrate of soda previously caused to deposit in the solution vessel;
(equivalents of potassa and nitrate of soda are used) evaporation is carried on
gently, and the boiling fluid drawn off into a crystallizer, where the greater
part of the saltpetre becomes crystallized by cooling; the mother water still
containing some saltpetre is highly evaporated and recrystallized; the solid
resultant kept from the air is thrown back into the solution for the next
crystallization, while the liquid portion forms a strong solution of caustic soda,
with hardly a trace of saltpetre, which may be evaporated and drawn off.
The washings-may-be-reduced,-and-presence of alkali neutralized by a few
drops of diluted nitric or hydrochloric acid, forming some traces of nitrate of
soda or chloride of sodium, the greater portion of which flows away in solution
before removing the saltpetre from the drying room.