Improvements in Manufacturing Metallic Fluorides.
Year: 1895

page_text: Date of Application, 29th Oct., 1895
Complete Specification Left, 28th July, 1893—Accepte!, 5th Sept., 1896
PROVISIONAL SPECIFICATION.
Improvements in Manufacturing Metallic Fluorides.
I WALTER MILLS of 20 Anstey Road Peckham London S.E. Analyst do
hereby declare the nature of this invention to be as follows:-
In order to manufacture metallic fluorides by this invention, I prepare ammonic
fluoride by heating either ammonic sulphate or ammonic chloride with calcic
fluoride; I prefer to employ the former. The ammonic fluoride sublimes and may
be readily condensed to a white amorphous powder. If I wish to prepare for example
sodic fluoride I then heat this ammonic fluoride with common salt; ammonic
chloride sublimes leaving sodic fluoride behind. Or I treat an aqueous solution of
common salt preferably hot, with the ammonic fluoride; in this case sodic fluoride
is precipitated and ammonic chloride remains in solution. In like manner I may
treat an aqueous solution of sodic sulphate, the by-product in this case being
ammonic sulphate. When using aqueous solutions of salts of the metals whereof I
desire to prepare the fluorides, I sometimes lead into the solutions the elements of
ammonic Huoride, i.e. ammonia gas and hydric fluoride; or I may lead the uncondensed
vapour of ammonic fluoride direct into the solutions. I thus produce the same
results as by using condensed ammonic fluoride prepared as aforesaid. By suitably
modifying the proportions of the ingredients used, I prepare by this invention
a variety of important metallic fluorides.
Dated this 20th der of October 1805
WALTER MILLS.
Improvements in Manufacturing Metallic Fluorides.
1 WALTER MILLS of 20 Anstey Road Peckham London S.E. Analyst 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 :-
My invention for the preparation of metallic fluorides depends upon the action of
anmonic fluoride, or of the components thereof viz. ammonia and hydric fluoride,
upon metallic salts or their aqueous solutions.
In order to prepare ammonic fluoride, I mix together finely powdered ammonic
sulphate and calcic fluoride (fluor spar) in a similar state of division, and then
heat the mixture gently to a temperature of about 350 C. in a subliming retort.
The lower part of this apparatus may be made of cast iron covered internally with
a thin coating of calcic sulphate, but I prefer to construct the upper part of lead,
and to keep it as cool as is conveniently practicable. A satisfactory method of
doing this is to make the upper part of the retort concave, keeping this concavity
full of water. On heating the apparatus as aforesaid a reaction takes place which
is indicated by the equation

page_text: In the case of those metallic salts, which give aqueous solutions that are not
precipitated by ammonia, viz. the salts of sodium, potassium barium and stroutium,
I prefer to mix the proper quantity of ammonia with the aqueous solution and
then to treat it with hydric fluoride either in the gaseous state or dissolved in
water the gas would seem to produce the best results. But in the case of other
aqueous solutions of metallic salts, which give precipitates when treated with
ammonia, such as the salts of aluminium, chromium, manganese &c., I add to the
solution of the salt ammonic fluoride, either solid or dissolved in water, or I take
an aqueous solution of ammonic fluoride and add the finely ground metallic salt
thereto, or I treat the solution of the metallic salt first with hydric fluoride and
then with ammonia in the manner hereinafter described.
I will now describe the method by which I prepare sodic fluoride; this method
is applicable to all those aqueous solutions of metallic salts which are not
precipitated by ammonia, it being understood however that, instead of the process
I am now about to describe, I may add ammonic fluoride, either dry or dissolved in
water, to such aqueous solutions.
I take salt brine weak enough to hold in solution the ammonic chloride that is
produced by the reaction and to absorb the proper quantity of ammonia gas
without serious loss. I then blow into this brine ammonia gas in about the
proportion indicated by the ensuing equation; it is desirable to have a slight
excess of ammonia in the brine, in order to prevent the formation of acid sodic
fluoride (NaHF₂). After the proper quantity of ammonia has been thus dissolved
in the brine I introduce into the mixture, which I keep in a state of gentle
agitation, gaseous hydric fluoride. In these circumstances sodic fluoride is
precipitated according to the equation :-
NaCl + NH3 + HF = NH¸Cl + NaF.
I also attain the same result by agitating ground common salt with an aqueous
solution of ammonic fluoride, or by adding ammonic fluoride to an aqueous
solution of sodic chloride.
It would appear that, when an aqueous solution of sodic chloride and ammonia is
treated with gaseous hydric fluoride, the precipitate of sodic fluoride is practically
ins luble and anhydrous; when the same solution say of a specific gravity of
about 1126 is treated with aqueous hydric fluoride say of a specific gravity of
about 115 an hydrated fluoride is precipitated which seems to be soluble
in about 32 parts of water. When an aqueous solution of ammonic fluori le is
treated with finely ground sedie chloride at the ordinary temperature the precipitate
is gelatinous and more soluble than when hot aqueous solutions of ammonic fluoride
and sodic chloride are mixed. I find in practice that the product when aqueous
solutions of sedie chloride and an monic fluoride are mixed at about 50 C. and then
heated with stirring to about 80 C. is much the same as when gaseous hydric
fluoride is led into an aqueous solution of sodic chloride and ammouia in the cold.
Generally, when anhydrous fluorides are required the thermal conditions of the
reactions by which they are produced must be somewhat high.
Instead of using an aqueous solution of sodic chloride as aforesaid I may use an
aqueous solution of sodic sulphate in like manner and with the same resulting
precipitate, in accordance with the equation
It is to be observed that an aqueous solution of sodic sulphate is not precipitated
by animonic fluoride, tut if sodic sulphate in fine powder bo agitated with au
aqueous solution of ammonic fluoride, preferably hot, sodic fluoride is precipitated.
The same may be said of potassic sulphate, but the aqueous slutions of both these
sulphates give precipitates of fluorides when treated first with ammonia and then
with hydric fluoride or vice cerca. Fluoride of potassium is however much more

page_text: soluble than fluoride of sodium, and generally the behaviour of these sulphates is
less advantageous than that of the corresponding chlorides.
In like mauner to the methods by which I prepare sodic fluoride I prepare the
fluoride of potassium; the sulphates of strontium and barium being practically
insoluble in water, I prepare the fluorides of these metals from their respective
chlorides, in the same way that I prepare sodic fluoride.
The methods by which I treat aqueous solutions of the chloride or sulphate of
aluminium are typical of the methods by which I prepare fluorides from aqueous
solutions of the salts of those metals which are precipitated by ammonia. An
aqueous solution of aluminic chloride may be conveniently prepared by precipitating
an aqueous solution of aluminic sulphate with ammonia, and then dissolving the
precipitate in hydrochloric acid. The presence of ammonic sulphate in the solution
of aluminic chloride thus produced does not prejudicially affect the reaction which
takes place when ammonic fluoride is added to it and is expressed by the following
equation:-
or 1 may add hydric fluoride to an aqueous solution of aluminic sulphate and then
treat the mixture with ammonia, or the sulphate or chloride of aluminium inay be
added in a state of powder to aqueous ammonic fluoride. Ammonia alum may be
employed advantageously instead of aluminic sulphate where a very pure fluoride
of aluminium is required in large quantities, as commercial ammonia alum is almost
chemically pure.
In like manner to aluminic fluoride I prepare the fluoride of chromium from
either hydrated chromic chloride, chromic sulphate, or chrome alum. Similarly
I prepare the fluorides of copper, magnesium, manganese, ani zinc from their
respective sulphates or chlorides.
Many compound fluorides may be prepared by this process; thus artificial
cryolite may be precipitated from mixtures of the aqueous solutions of the
sulphates of aluminium and sodium, or from similar mixtures of the chlorides of
these metals. In the former case bydric fluoride is first added to one of the
sulphates, the other sulphate is then added, and the mixture is treated with
ammonia. The double fluoride of magnesium and potassium may also be prepared
in like manner and with the like precautions. Similarly many other compound
fluorides may be prepared.
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:
1. The production of ammonic fluoride by heating a mixture of ammonic sulphate
and calcic fluoride (fluor spar) substantially as described.
2. The method of preparing metallic fuorides from aqueous solutions of the
chlorides of aluminium, barium, chromium, copper, magnesium, manganese,
potassium, sodium, strontium, or zinc, by adding to the respective solutions
ammonic fluoride, substantially as described.
3. The method of mixing the chlorides of aluminium, barium, chromium, copper,
magnesium, manganese, potassiuin sodium, strontium, or zinc, whether hydrated or
anhydrous, with aqueous solutions of ammonic fluoride, and thus preparing the
respective metallic fluorides, substantially as described.
4. The method of mixing the sulphates of aluminium, chromium, copper,
magnesium, manganese, potassium, sodium, or zinc, whether hydrated or anhydrous,

page_text: with aqueous solutions of ammonic fluoride, and thus preparing the respective
metallic fluorides, substantially as described.
5. The method of mixing ammonia with aqueous solutions of the chlorides of
barium, potassium, sodium, or strontium, treating the mixture with hydric fluoride,
and thus preparing the respective metallic fluorides, substantially as described.
6. The method of mixing hydric fluoride with aqueous solutions of the sulphates
of aluminium, chromium, copper, magnesium, manganese, potassium, sodium, or
zinc, treating the mixtures with ammonia, and thus preparing the respective
metallic fluorides, substantially as described.
7. The method of adding ammonic fluoride to aqueous solutions of the sulphates
of aluminium, chromium, copper, magnesium, manganese, or zinc, and thus preparing
the respective metallic fluorides, substantially as described.
8. The production of compound fluorides by treating mixtures of metallic salts
with ammonic fluoride or its components, substantially as described.
Dated this 28th day of July 1896.
WALTER MILLS.