Improvements in the Manufacture of Zinc White.
Year: 1896

page_text: Improvements in the Manufacture of Zinc White.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
45 Southampton Buildings, in the County of Middlesex, do hereby declaro the
nature of this invention to be as follows:-
It is known that zinc white tends to gradually replace white lead in painting and
the advantage which the former product possesses over the latter need not be
specially referred to here.
Up to the present time a defective method of producing zinc white has been
employed. The zinc heated in earthen retorts to about 1050 degrees Centigrade
becomes distilled and the vapours are burnt in a current of air; oxide of zinc is
thus formed which is collected in large chests or receptacles provided for the
purpose.
This process is accompanied by several inconveniences; it being first of all
troublesome; the quantity of fuel used is considerable, the earthen retorts become
rapidly worn; the zinc must be as pure as possible and its cost therefore is very
high; however accurately the apparatus be constructed it allows a considerable
proportion of zinc vapours to escape; the yield is only 105 kilogrammes of oxide
for 100 kilogrammes of metal; the process is further defective in as much as it is
impossible to manufacture a zinc which is entirely free from lead, and this lead
disengaged and carried along in the process of distillation, is again taken by the
zinc white which after the lapse of a short time becomes yellow tint under the
influence of sulphurous emanations.
We have devised an economical process of manufacturing zinc white, by which a
purer product than that by the previous process is obtained.
I will first proceed to describe this improved process and subsequently to point
out its advantages.
In a closed sheet iron vessel lined with lead, I treat zinc residues of the quality
known by the name of "rag-picker's zinc," with chlorhydric acid and thus obtain:
The hydrogen is collected and may be utilized either as a fuel in the workshop,
0 or as an illuminating agent. I make sure that the solution of chloride of zinc thus
obtained does not contain more than 0.5 per cent. of iron; should a larger quantity
of this latter substance be present, I eliminate it by the aid of oxide of zinc.

page_text: The white or milk thus formed is passed into a decanting vessel, where it is
allowed to settle, I then decant and place the precipitate in a quantity of boiling
water equal in weight to the said precipitate; I pass the whole product thus
obtained into a second vessel provided with a stirring device, which constantly
maintains the precipitate in suspension while a leaden coil heated by steam
maintains the mixture at a temperature of from 70 to 80 degrees Centigrade. From
this vessel the milk is passed into turbines provided with a tissue of very close
structure, where it loses all its water, which carries away with it tho whole of the
chloride of magnesium retained by the oxide of zinc.
The zinc white is subsequently placed in a drying chamber heated to 120 degrees
Centigrade in which the desiccation is completed.
It is known that the hydrated chloride of magnesium has the characteristic
quality of becoming decomposed, under the influence of heat, into chlorhydric acid,
which is disengaged and maguesia which remains.
The solution by means of which the oxide of zinc was recovered and the washing
waters are mixed and evaporated at a low temperature in a triple acting or triple
effect apparatus, until the said solution attains a density of 1·4; it is subsequently
placed in a special furnace where it is subjected to a temperature of about
250 degrees Centigrade. The chlorhydric acid and the magnesia thus obtained
may serve in fresh operations.
My process possesses the following advantages:
The hydrogen obtained, in reality disengaged from the water, replaces coal, wood
or the like as fuel, now, this hydrogen does not cost anything. When sold as an
illuminating agent its value will always be higher than that of coal or the like
which could otherwise be employed.
The material undergoes only a slight deterioration; repair is seldom required.
I employ zinc of very inferior quality which may be impure; as the chlorhydric
acid does not attack the lead the presence of this metal in the oxide of zinc need
not be feared; the elimination of iron is provided. The zinc, such as I employ
costs 40 per cent. less than the zinc which serves for the manufacture of zinc white
in the dry way.
All our operations as far as they refer to the treatment of the liquids may
carried out by the aid of machines, the use of manual labour is exceedingly limited,
so that the cost of labour is very slight.
As the oxide of zinc, during the whole course of operations is mixed with liquids
it cannot escape into the atmosphere in the form of dust, and as the zinc is not
heated it can not be lost in the state of vapour. The yield therefore is higher than
that obtained in the dry way; it being equivalent to 120 parts of oxide for
100 parts of metal.
We may substitute. for magnesia, any oxide which is capable of precipitating
zinc from its chlorhydric solutions in the state of oxide of zinc while giving a
chloride which is decomposable or volatilizable by heat.
Dated this 24th day or October 1000.

page_text: I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
45 Southampton: Buildings,, in the County of Middlesex, 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 :-
It is known that zinc white tends to gradually replace white lead in painting and
the advantage which the former product possesses over the latter need not be specially
referred to here.
Up to the present time a defective method of producing zine white has been
employed. The zinc heated in earthen retorts to about 1050 degrees Centigrade
becomes distilled and the vapours are burnt in a current. of air; oxide of zinc
is thus formed which is collected in large chests or receptacles. provided for the
purpose.
This process is accompanied by several inconveniences; it being first of all trouble-
some; the quantity of fuel used is considerable, the earthen retorts become rapidly
worn; the zinc must be as pure as possible and its cost therefore is very high;
however accurately the apparatus be constructed it allows a considerable proportion
of zinc vapours to escape; the yield is only 105 kilogrammes of oxide; the process is
further defective inasmuch as it is impossible to manufacture a zinc which is entirely
free from lead, and this lead disengaged and carried along in the process of
distillation, is again received in the zinc white which after the lapse of a short
time becomes yellow under the influence of sulphurous emanations.
We have devised an economical process of manufacturing zinc white, by which a
purer product is obtained than that by the previous process."
I will first proceed to describe this. improved process and subsequently to point
out its advantages.
In a closed sheet iron vessel lined with lead, I treat zine residues of the quality
known by the name of "rag-picker's zinc," with chlorhydric acid and thus obtain:
Zn+HC1 Zn CI+H...
The hydrogen is collected and may be utilized either as a fuel in the work-shop, or
as an illuminating agent. I make sure that the solution of chloride of zinc thus
obtained does not contain more than 0.5 per cent. of iron; should a larger quantity
of this latter substance be present, I eliminate it by the aid of oxide of zinc.
This solution is filtered; I then test, by the means of nitrate of silver, its yield of
free or combined chlorhydric acid, subsequently I raise the temperature of the
solution to the boiling point and add 54 parts of magnesia to 100 parts of chlorhydric
acid; I thus obtain:
ZnC1+MgO ZnO + MgCl...
The white or milk thus formed is passed into a decanting vessel, where it is allowed
to settle, I then decant and place the precipitate in a quantity of boiling water equal

page_text: its water, which carries away with it the whole of the chloride of magnesium
retained by the oxide of zinc.
The zinc white is subsequently placed in a drying chamber heated to 120 degrees
Centiade in which the desiccation is completed.
It is known that the hydrated chloride of magnesium has the characteristic
quality of becoming decomposed, under the influence of heat into chlorhydric acid,
which is disengaged and magnesia which remains.
The solution by means of which the oxide of zinc was recovered and the washing
waters are mixed and evaporated at a low temperature is a triple acting or triple
effect, apparatus, until the said solution attains a density of 14; it is subsequently
placed in a furnace where it is subjected to a temperature of about 250 degrees
Centigrade. The chlorhydric acid and the magnesia thus obtained may serve in
fresh operations.
My process possesses the following advantages:
The hydrogen obtained, in reality disengaged from the water, replaces coal, wood
or the like as fuel, now, this hydrogen does not cost anything. When sold as an
illuminating agent its value will always be higher than that of coal or the like which
would otherwise be employed.
The material undergoes only a slight deterioration; repair is seldom required. I
employ zinc of very inferior quality which may be impure; as the chlorhydric acid
does not attack the lead the presence of this metal in oxide of zinc need not be
feared; the elimination of iron is provided for. The zinc, such as I employ costs
40 per cent. less than the zinc which serves for the manufacture of zinc white in the
dry process.
All my operations as far as they refer to the treatment of the liquids may be carried
out by the aid of machines, the use of manual labour is exceedingly limited, so that
the cost of labour is very slight.
As the oxide of zinc, during the whole course of operations is mixed with liquids
it cannot escape into the atmosphere in the form of dust, and as the zinc is not
heated it cannot be lost in the state of vapour. The yield therefore is higher than
that obtained in the dry process; it being equivalent to 120 parts of oxide for
100 parts of metal.
I may substitute for magnesia, any oxide which is capable of precipitating zinc
from its chlorhydric solutions in the state of oxide of zinc while giving a chloride
which is composable or volatilizable by heat.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is :-
The manufacture of zinc white precipitated by means of magnesia, or of any other
oxide giving oxide of zinc in reacting upon chloride of zine and a chloride decomposable
or volatilisable by heat.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.