Year: 1896

page_text: Date of Application, 31st July, 1896
Complete Specification Left, 29th Apr., 1897-Accepted, 29th May, 1397

page_text: adopted-Finely levigated zinc oxide is stirred into the solution of zinc sulphate
and chlorine gas passed into the liquid (or a saturated solution of chlorine gas in
water is added). When a sufficient quantity of chlorine is present and by continuous
stirring the zinc oxide is obtained in a finely divided state in the solution, the iron
cobalt and manganese which may be present as an impurity are within a few hours
precipitated as sesqui-oxides and peroxides respectively. The precipitate which
gradually settles down contains in addition such portion of the oxide of zinc as has
not gone into solution as chloride of zinc. If an unnecessarily large proportion of
zinc oxide has been avoided and the iron has been for the most part previously
removed, the precipitate is mainly composed of cobalt sesqui-oxide and manganese
dioxide. After filtering in the filter press the precipitate may be used in producing
chlorine to be employed as described. For this purpose the precipitate is treated
either with hydrochloric acid or with a mixture of sulphuric acid and common salt.
Dated this 31st day of July 1896.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered l'atent Agents.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Zino Pigments.
I ALEXANDER MELVILLE CLARK, of the Firm of A. M. & Wm. Clark, of
53 Chancery Lane in the County of Middlesex, Fellow of the Chartered Institute
of Patent Agents, do hereby declare the nature of this invention (a communication
to me by Professor Dr. Wilhelm Hampe and Professor Dr. Carl Schnabel,
both of Clausthal University, Clausthal, Hanover. in the Empire of Germany) and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
It is well known that zinc oxide can be coloured by certain metallic oxides, and
pigments so constituted have been known in the arts for a considerable time.
The object of the present invention is to obtain such zinc pigments in a cheaper
and more convenient manner than heretofore.
According to this invention I obtain a thoroughly intimate mixture of sulphate
of zinc and a sulphate of a metal whose oxide is to be the source of the colour of
the pigment (bereinafter referred to as the sulphate of the colouring metal). This
intimate mixture is thoroughly commingled with finely comminuted carbon,
preferably wood charcoal, and the mixture so obtained is heated to a carefully
gauged temperature of 650° C.
It has previously been discovered that when an intimate mixture of dehydrated
zinc sulphate and finely comminuted carbon is heated to this carefully gauged
temperature, a chemical change, resulting in the formation of zinc oxide, proceeds
according to the equation:-
ZnSOC ZnO + CO + SO,
When, in addition to sulphate of zinc, there is present the sulphates of certain
anets ls whose oxides colour zinc oxide, it has been discovered that the sulphate of
such metal is also converted into oxide and a pigment results.
In carrying out this invention I proceed as follows:-I dissolve the quantity of
the sulphate of the colouring metal required for a given charge in about four times
its weight of water and add this solution to crystallized zinc sulphate. The solution
of the sulphates obtained (by heating, if necessary), is evaporated and the mixture
of the sulphates dehydrated. The dehydrated mixture of the sulphates is then
mixed with finely-comminuted carbon and heated as described above. It has been

page_text: found to be advantageous to allow the oxides to continue glowing at a low heat in
a current of air for some time after the disengagement of sulphurous acid has
ceased.
The best results have so far been obtained by using as the sulphate of the
colouring metal the sulphates of nickel, cobalt, manganese, and iron. In some cases
mixtures of two of these sulphates with zinc sulphate have been employed; in
others only one such sulphate mixed with zinc sulphate has been used. By varying
the proportions of the sulphate of the colouring metal or metals relatively to the
zinc sulphate, pigments of varying shades have been produced and according as one
or other of the sulphates or a mixture of two was used pigments of different colours
have been produced.
Having stated the nature of the invention, I will further illustrate it by giving
an account of the sulphates of the colouring metals employed in obtaining
pigments, and describe the variations in colour or shade of colour which can be
obtained by varying the nature of the sulphate of the colouring metal employed, or
by employing mixtures of two sulphates of colouring metals in varying proportions.
I premise however that these details are given only by way of illustrating the
application of the invention and I do not limit myself to them.
Green pigments with a shade of blue are obtained when sulphate of cobalt is
employed as the sulphate of the colouring metal. The proportions used were for
one thousand kilogrammes of crystallized zinc sulphate, in one case 6.16 kilogrammes
of crystallized sulphate of cobalt, and in another case twice this quantity viz. :-
12:32 kilogrammes; in a third case for the same proportion of crystallized zinc
sulphate 154 kilogrammes of the sulphate of cobalt, and in a fourth case
30-8 kilogrammes were used.
In obtaining green pigments with a yellow shade, sulphate of nickel together
with sulphate of cobalt were employed as the sulphates of the colouring metals.
Here the proportions in which the sulphates were employed were the following:-
For one thousand kilogrammes of crystallized zinc sulphate, 9 kilogrammes of
crystallized sulphate of nickel and 30-8 kilogrammes of sulphate of cobalt, in one
case, and 15 kilogrammes of sulphate of nickel and 46-2 kilogrammes of sulphate of
cobalt, in another case.
When sulphate of manganese together with sulphate of cobalt is used, the shade
of the pigment is olive. The precise shade of olive varies according to the total
quantity of these sulpbates employed in proportion to that of the crystallized zinc
sulphates, and further varies according to the proportions, inter se, in which the
sulphates of manganese and cobalt are used. In one case the proportions used
were 12-32 kilogrammes of sulphate of cobalt and 6.16 kilogrammes of crystallized
sulphate of manganese to one thousand kilogrammes of crystallized sulphate of
zinc.
Yellow pigments with a greenish shade are obtained when sulphate of nickel is
used as the sulphate of the colouring metal. The nickel sulphate was, in one case,
in the proportion of three kilogramme to one thousand kilogrammes of the
crystallized zinc sulphate, and in another case in the proportion of twelve kilo-
grammes to one thousand kilogrammes of the crystallized zinc sulphate.
Yellow to brownish pigments are obtained when sulphate of manganese is
employed as the sulphate of the colouring metal. The proportions which have
been employed are for one thousand kilogrammes of crystallized sulphate of zinc,
three, six, nine, twelve, and fifteen kilogrammes of crystallized sulphate of
manganese.
In obtaining reddish pigments sulphate of iron has been used as the sulphate of
the colouring metal. The proportions which have been employed are for one
thousand kilogrammes of crystallized sulphate of zinc, nine, fifteen, and thirty
kilogrammes of crystallized sulphate of iron.
Greyish green pigments are obtained when sulphate of cobalt and sulphate of
iron are used together as sulphates of colouring metals. These sulphates have been
employed in the following proportions :-For one thousand kilogrammes of

page_text: crystallized zinc sulphate, 308 kilogrammes of sulphate of cobalt and 30 kilo-
grammes of sulphate of iron.
In the production of the more delicately tinted pigments it is advisable to purify
the zinc sulphate to be used, and for this purpose the following method has been
adopted Finely levigated zinc oxide is stirred into the solution of zinc sulphace
and chlorine gas passed into the liquid (or a saturated solution of chlorine gas in
water is, added). When a sufficient quantity of chlorine is present and by
continuous stirring the zinc oxide is obtained in a finely divided state in the
solution, the iron cobalt and manganese which may be present as an impurity are
within a few hours precipitated as sesqui-oxides and peroxides respectively. The
precipitate which. graduaily settles down contains in addition such portion of the
oxide of zinc as has not gone into solution as chloride of zinc. If an unnecessarily
large proportion of zinc oxide has been avoided and the iron has been for the most
part previously removed, the precipitate is mainly composed of cobalt, sesqui-oxide
and manganese dioxide. After filtering in the filter press, the precipitate may
be used in producing chlorine to be employed as described. For this purpose the
precipitate is treated either with hydrochloric acid or with a mixture of sulphuric
acid and common salt.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
The herein described method or process of obtaining pigments, consisting in
preparing an intimate mixture of dehydrated sulphates of zinc and of one or more
of such metals as form oxides which when heated with zinc oxide impart a colour
to it, thoroughly commingling the mixture so prepared with finely comminuted
carbon, and subjecting the whole to a carefully gauged temperature of 650° C.
substantially as described.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.