IMPROVEMENTS IN THE MANUFACTURE OF CARBONATE OF STRONTIA
Year: 1883

page_text: LETTERS PATENT to David Urquhart of N° 4 The Sanctuary Westminster
in the County of Middlesex for an Invention of " IMPROVEMENTS IN THE
MANUFACTURE OF CARBONATE OF STRONTIA "
PROVISIONAL SPECIFICATION left by the said David Urquhart at the Office
of the Commissioners of Patents on the 15th January 1883.
"
DAVID URQUHART of N° 4 The Sanctuary Westminster in the County of
Middlesex "IMPROVEMENTS IN THE MANUFACTURE OF CARBONATE OF STRONTIA
This Invention relates to the manufacture of Carbonate of strontia from sulphate
of strontia or Celestine.
I take the sulphate and grind it into a fine powder and then boil it with the
black-ash liquor from the manufacture of carbonate of soda. This liquor contains
carbonate of soda, caustic soda and some sulphides etc, and by it the sulphate of
strontia is decomposed and carbonate of strontia and caustic strontia are formed,
and sulphate of soda.
The precipitated carbonate of strontia is then thoroughly washed to remove the
soda salts, and dried. The wash liquors and the first liquor are treated with
carbonic acid to recover the caustic strontia which is in solution (if there is
sufficient present to make it worth while) and they are then evaporated down and
sulphate of soda obtained from them.
Or I mix the carbonate of soda obtained by evaporation from the black ash
liquors with finely powdered sulphate of strontin and coal or sawdust or other
carbonaceous substance and roast the mass in a suitable furnace or in retorts.
The roasted mass which is usually run to a slag I treat with water to remove
the sulphate of soda, which is afterwards recovered, and the carbonate of strontia
remains.
When the natural sulphate of strontia contains much iron and alumina it is
advisable to treat the powdered ore with sulphuric acid and wash it with water

page_text: before treating it with the black-ash liquor or the solid matter obtained by
evaporation thereof as above described.
According to another method of making carbonate of Strontia, I roast the sulphate
mixed with precipitated alumina in the presence of hydrogen or of superheated steam.
Sulphuric acid is given off and an aluminate of strontia formed. This operation
can best be done in retorts.
The aluminate of strontia is afterwards decomposed by carbonic acid or by
carbonate of soda or liquors containing the same or other alkaline carbonates.
The aluminate of strontia is also obtained if the raw sulphate is first roasted
with coal and converted into sulphide

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said David Urquhart in the Great Seal Patent Office on the 6th July
1883.
DAVID URQUHART of No. 4 The Sanctuary, Westminster in the county of
Middlesex IMPROVEMENTS IN THE MANUFACTURE OF CARBONATE OF STRONTIA
I boil finely powdered sulphate of strontia in a suitable vessel with the black-
ash liquor obtained in the course of the manufacture of carbonate of soda by the
Leblanc process.
This liquor contains carbonate of soda, caustic soda and some
sulphide. The proportions of liquor and sulphate of strontia which I use depend
on the amount of carbonate of soda dissolved in the liquor, as there must be more
carbonate of soda present than the equivalent required to decompose the sulphate
of strontia. In this operation, the sulphate of strontia is converted into carbonate,
an equivalent quantity of the carbonate of soda from the liquor being converted
into sulphate of soda. The precipitate of carbonate of strontia is then thoroughly
washed to remove the soda salts, and then dried, preferably in a furnace and at a
low dull red heat, with the admixture, if the per centage of sulphide present is too
high, of some carbonaceous substance, such as sawdust. Although I have
mentioned black-ash liquor as the solution of carbonate of soda which I employ on
account of its cheapness, it is obvious that any other available solution of carbonate
of soda will answer the purpose, and when the carbonate of stronția is required
pure, I use a pure solution of carbonate of soda. The liquors from the boiling pan
I boil down to dryness or nearly so and thus obtain the sulphate of soda
Or I mix the black-ash itself (obtained from the boiling down of the black-ash
liquors in the Leblanc process) with powdered sulphate of strontia (the proportion
of each being so regulated that there is an excess of carbonate of soda of about 10°)
and with powdered coal or charcoal or sawdust or other carbonaceous substance,
the quantity of which will depend upon the amount of sulphides in the black-ash,
and I roast the mixture in a suitable furnace at a bright red heat. As the black-
ash, when obtained, is usually moist, I sometimes place it and the charcoal in the
furnace first, and heat it up before adding the sulphate of strontia.
The mixture, which usually melts or runs to a slag, I treat with water to
remove the soda salts, and then I dry the carbonate of strontia and boil down the
sulphate of soda liquors, When the sulphate of strontia contains much iron and
alumina or other impurities, it is advisable, if pure carbonate of strontia is required,
to boil it with dilute sulphuric or other acid before treating it by either of the .
methods described above.
According to another method, I mix the finely ground sulphate of strontia with
precipitated alumina and roast the mixture in retorts, through which I cause
super-heated steam to pass. Sulphuric acid is given off, which can be condensed
and an aluminate of Strontin is formed.
I grind the aluminate and suspend it in water, either hot or cold, through which
I then force carbonic acid. I sometimes do this under pressure. The aluminate
is decomposed, and carbonate of strontia precipitated, and alumina. I separate the
carbonate from the alumina by any means of washing, such as buddles or riffles,
the lighter alumina being washed out and settled, when it can be used over again.
Or I treat the aluminato with an alkaline carbonate, by fluxing in a furnace, thus
forming carbonate of strontia and an alkaline aluminate, which I separate by
washing. The liquors from this I boil down to obtain the alkaline aluminate. The
quantity of alkaline carbonate should exceed an equivalent, and may have addition
of caustic alkali,

page_text: Instead of roasting sulphate of strontia with alumina, I sometimes convert the
sulphate into sulphide by roasting it with coal or carbonaceous substances, and
then treat this sulphide, either as it comes from the furnace or after lixiviating
it out and boiling it down, with alumina and superheated steam as described
above
'
Having thus described the nature of my invention and in what manner the same
is to be performed, I hereby declare that I make no general claim to the production
of carbonate of soda by treating sulphate of strontia with alkaline carbonate, but I
claim―
:
First The manufacture of carbonate of strontia by treating sulphate of strontia
or Celestine with carbonate of soda, substantially as described.
Second: The manufacture of carbonate of strontia by mixing sulphate of strontia
or Celestine with black-ash & carbonaceous substances, roasting the mixing
and treating the product substantially as herein described.'
Third: The manufacture of carbonate of strontia by converting the sulphate or
the sulphide into aluminate and decomposing the same by carbonic acid
or an alkaline carbonate substantially as described.
In Witness whereof I the said David Urquhart have hereunto set my hand
and seal this thirtieth day of June in the year of our Lord, one thousand eight
hundred and eighty-three