An Improved Paint, specially applicable as a Substitute for White Lead, Zinc White, and the like, and Process of Manufacturing the same.
Year: 1895

page_text: Date of Application, 6th Feb., 1895-Accepted, 16th Mar., 1895
COMI DELE
KITIVATION.
An Improved Paint, specially applicable as a Substitute for White
Lead, Zinc White, and the like, and Process of Manufacturing
the same.
I, RUDOLF ALBERTI of 11 Breiteweg Magdeburg in the Kingdom of Prussia,
Germany, Chemist, 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 :-
This invention has for its object a rapidly drying paint of good body, specially
applicable as a substitute for white lead, zinc white, and the like, and process of
manufacturing the same.
In carrying out the invention any suitable quantity of ground sulphate of zinc
is thoroughly mixed with an equivalent quantity of calcium carbonate, calcium
oxide or barium carbonate, and this mixture is exposed to a moderate red heat
in a suitable furnace for several hours. The whole mass shortly dissolves into its
water of crystallisation, whereby an extremely fine subdivision and mixture of the
substances takes place. The heat being now increased, the mixed mass swells or
boils up, whilst the water of crystallisation evaporates, and when the heating is
continued the mass is decomposed into oxide of zinc and sulphate of calcium
respectively, or when barium carbonate is used, into oxide of zinc and sulphate of
barium, whilst the carbonic acid is volatilised and escapes.
This decomposition of the two substances takes place at a considerably lower
temperature, when the substances are mixed (as herein before described), than
when the substances are each of them heated separately, that is to say, sulphate
of zinc alone, calcium carbonate alone and barium carbonate alone, require for
their decomposition into oxide of zinc and sulphuric acid, or into carbonic acid
and oxide of calcium, or into carbonic acid and oxide of barium, respectively, a
very much higher temperature than is necessary for the decomposition of a mixture
of these substances. For the decomposition of the greatest part of this mixture
it is sufficient to heat it over an ordinary good Bunsen burner for some time at a
red heat, whilst at the same temperature the decomposition of sulphate of zinc
alone and of calcium carbonate alone, only takes place to a small extent, and the
decomposition of barium carbonate does not take place at all.
The same results are obtained if the substances be heated in a common heating
furnace instead of on a Bunsen burner, whilst the decomposition of the barium
carbonate alone only takes place by heating it in a specially constructed furnace,
to a temperature four or six times higher than that employed in a common heating
furnace.
The heating of the mixture in the furnace is continued until only a small
quantity of undecomposed sulphate of zinc, calcium carbonate or barium carbonate
is still present, as thereby the drying quality of the paint is very greatly
improved.
After cooling, the mass which is obtained by this process of beating is ground,
the softness of the same enabling a high degree of fineness to be obtained. The
paints thus obtained (zinc-anhydride and zinc-baryta) possess a good body which
is obtained by the extremely fine subdivision of the paint produced in this process
as described by fusion of the mixture of the substances and the gradual decom-
position at a moderate temperature. These paints also possess excellent drying
qualities in consequence of the small quantity of undecomposed sulphate of zinc

page_text: finely distributed over the whole mass.
These paints are an excellent substitute
for lead and zinc paints and are of a greater technical importance than the lead
and zinc paints hitherto known. If made from pure raw materials they may be
used as white or yellowish white paints and if made from less pure materials they
may be used alone or mixed with other colours as good oil paints more particularly
as rapidly drying ground or floor paints.
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 :-
1. An improved process for the manufacture of paint, consisting in heating a
mixture of equivalent quantities of sulphate of zinc and calcium carbonate or
calcium oxide or barium carbonate gradually to a moderate temperature until the
carbonic acid is almost entirely volatilised, and in afterwards grinding the substance
thus produced substantially as hereinbefore described.
2. An improved paint specially applicable as a substitute for white lead, zinc
white and the like, formed of a mixture of sulphate of zinc with an equivalent
quantity of calcium carbonate, calcium oxide or barium carbonate, said mixture
being fused and subsequently ground substantially as hereinbefore described.
Dated this 5th day of February 1895.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.