IMPROVEMENTS IN THE MANUFACTURE OF SULPHIDE OF ZINC AND OF HYDRATE OR OTHER SALTS OF BARYTA OR STRONTIA
Year: 1884

page_text: I HENRY KNIGHT of 14 Enton Street, Liverpool, in the County of Lancaster,
Paint Manufacturer, do hereby declare the nature of my said invention for
"IMPROVEMENTS IN THE MANUFACTURE OF SULPHIDE OF ZINC AND OF HYDRATE
OR OTHER SALTS OF BARYTA OR STRONTIA," to be as follows :—
Hitherto barium or strontium sulphide and zinc sulphate have been caused to
re-act upon each other causing a double precipitate intimately mixed, which after
calcination has been sold as a pigment. Now it is found that unless zinc sulphide
be much more in excess than by this method the resulting pigment is poor, but if
zinc chloride instead of zinc sulphate be used in whole or in part to effect this
object the alkaline or alkaline earth base used is wasted as a chloride.
Now my invention is designed to get the pure sulphide of zinc and yet get the
alkaline earth base as a valuable product instead of running it to waste as chloride.
I therefore dissolve sulphide of barium or sulphide of strontium and by admixture
with a solution of chloride of zinc in suitable proportion to precipitate the whole
of the sulphur of the sulphide of barium or sulphide of strontium obtain a
solution of chloride of barium or chloride of strontium, to which after decantation
or filtration from the precipitate of sulphide of zinc, and concentration by
evaporation, I add caustic soda or caustic potash. Such precipitate as may form
impurities in the caustic alkali by chloride of barium or strontium solution,
I separate by decantation or filtration, and from the clear solution thus obtained,
hydrate of baryta or strontia crystallizes out on cooling; or in place of using
chloride of zinc at the first I use nitrate of zinc and precipitate by means of
sulphide of baryta or strontia, the resulting solution of nitrate of baryta or
strontia is then concentrated down and forms a very valuable bye-product. In a
similar manner almost every other valuable salt of baryta or strontia can be
obtained, a salt of soda or potash being used instead of hydrate of soda, or the
corresponding salt of zinc being used in the first instance, the only point to be
provided against being-not to employ any salts that shall form double precipitates,
but where the zinc and alkaline earth salts added together would produce a
double precipitate a salt or hydrate of soda must be used as an intermediator to
precipitate the one and then add the other to the resulting soda salt.

page_text: COMPLETE SPECIFICATION.
I, HENRY KNIGHT of 14 Eaton Street, Liverpool in the County of Lancaster,
Paint Manufacturer, do hereby declare the nature of my said invention for
İMPROVEMENTS IN THE MANUFACTURE OF SULPHIDE OF ZINC, AND OF HYDRATE
OR OTHER SALTS OF BARYTA OR STRONTIA " and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
Hitherto barium or strontium sulphide and zinc sulphate have been caused to
react upon each other causing a double precipitate intimately mixed, which after
calcination, has been sold as a pigment, now it is found that unless the proportion
of zinc sulphide is much greater than is yielded by this method, the resulting
pigment is poor, but if zinc chloride instead of zinc sulphate be used in whole or in
part, the alkaline earth base used is wasted as a chloride.
Now my invention is designed to produce pure sulphide of zinc, or a double
precipitate much richer in zinc sulphide than the ordinary double precipitate, and
yet obtain the alkaline earth base as a valuable product instead of running it to
waste as chloride.
For this purpose I take a solution of sulphide of barium or of strontium and add
thereto some other soluble salt of zinc than the sulphate which will not precipitate
the alkaline earth base, such as the chloride, nitrate or acetate or a mixed solution
of the sulphate, and one of these other salts of zinc in such proportions that the
sulphur in the sulphide of barium, and the zinc in the mixed salts shall be
in chemically equivalent proportions to form sulphide of zinc Zn S..
If chloride of zinc be used, a solution of chloride of barium, or chloride of
strontium is obtained, from which after decantation or filtration from the
precipitate and concentration by evaporation I obtain either chloride of barium or
chloride of strontium by crystallization, or bydrate of baryta or strontia by adding
caustic soda or potash, or sulphate of barium or sulphate of strontium by
precipitation with sulphuric acid, or a soluble sulphate. In this latter case I prefer
to use sulphate of zinc, as I thereby leave in solution chloride of zinc for
precipitation by a further quantity of sulphide of barium or of strontium. If
however in place of using chloride of zinc at the first, I use nitrate or acetate of
zinc, and precipitate by means of sulphide of barium or strontium, I obtain a
solution of nitrate or acetate of barium or, strontium, which after decantation
or filtration is concentrated and crystallized to yield nitrate or acetate of barium
or strontium,
In a similar manner almost any other valuable salt of barium or strontium can
be obtained, the corresponding salt of zinc being employed in the first instance.
In cases where the zinc and alkaline earth salt added together would produce a
double precipitate not desired, a salt or hydrate of soda or potash must be used as
an intermediator to precipitate the one, and then add the other to the resulting
soda or potash salt. The barium or strontium salt can in nearly all instances be

page_text: separated from the sodium or potassium salt, formed at the same time by
concentration and crystallization, the alkaline earth salt being as a rule much the
less soluble.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is
1st. The improvement in the manufacture of sulphide of zinc, and salts or hydrate
of baryta or strontia which consists in adding a solution of sulphide of barium or
of strontium to a soluble salt of zinc, which will not precipitate the alkaline earth,
or to a mixed solution of such salt and the sulphate of zinc in such proportion that
the sulphur in the sulphide of the alkaline earth and the zinc shall be in chemically
equivalent proportions and shall be precipitated by each other, whereby a
precipitate is formed composed wholly of sulphide of zinc, or of the alkaline earth
sulphate, and of zinc sulphide, the latter largely in excess of the amount formed
when sulphide of barium is precipitated by sulphate of zinc only, and a soluble
salt of the alkaline earth is obtained in solution, from which one or other of the
many valuable salts or the hydrate of the said alkaline earth can be readily
manufactured.
2nd. The manufacture of soluble salts of barium or of strontium by adding the
corresponding salt of zinc to a solution of sulphide of barium or of strontium and
after separating the precipitate formed, crystallizing or evaporating to dryness.
3rd. The process of manufacturing hydrate or sulphate of baryta or of strontia,
as a bye-product, which consists in adding chloride, acetate, or nitrate of zinc to a
solution of sulphide of barium or of strontium as the case may be, separating the
precipitate so as to obtain sulphide of zinc, adding hydrate of soda or of potash, or
as the case may be sulphuric acid or a soluble sulphate to the residual solution and
crystallizing out, or separating the precipitate formed.
°
Dated this thirteenth day of June 1885