Improvements in the Art of Preparing Hides or Skins for Tanning and in Liquid Compositions of Matter for Treating such Hides and Skins.
Year: 1898

page_text: Date of Application, 13th Dec., 1898-Accepted, 22nd Apr., 1899
COMPLETE SPECIFICATION.
Improvements in the Art of Preparing Hides or Skins for Tanning
and in Liquid Compositions of Matter for Treating such Hides and
Skins.
I, HENRY HOLMES, a citizen of the United States, residing at No. 52, East
Canal Street, in the City of Philadelphia, in the County of Philadelphia, and
State of Pennsylvania, Manufacturer, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement:
-
My invention has relation to a liquid composition of matter adapted to treat
hides or skins in a state or condition known as raw stock" and to prepare the
same for the tanning operation by swelling the fibre, softening the gristle and
dissolving the animal and other refuse matters therefrom.
My invention consists of a liquid composition of matter for treating hides or
skins in a raw state, composed of a solution of sodium sulphide having in suspen-
sion a demulcent, such as chalk or whiting, the composition comprising a bath,
wherein the hides or skins are immersed and agitated as hereinafter described
and claimed.
My composition consists of the following ingredients in about the proportions
stated, viz.
Sodium sulphide-100 lbs., more or less, as the same varies in strength;
Chalk or whiting-25 lbs., more or less, according to the nature of the hides
or skins to be treated; and
Water in sufficient quantity, say 80 gallons, more or less, to make the liquid
composition of matter the required strength to Baumè test, according to the
nature of the hides or skins to be treated.
The sodium sulphide in quantity about three ordinary busketsful, is first dis-
solved in water to obtain a solution of a strength varying from 20 to 6° Baumè
test, more or less; the strength varying with the nature of the hides or skins to
be treated.
The demulcent which is used is chalk or whiting, the same being used with
water in sufficient quantity, say 8 gallons, more or less, so that the liquid com-
position of matter will be of the required strength or Baumè test, to mix with say
one ordinary bucketful of the demulcent. This mixture is then added to the
previously prepared sodium sulphide solution. The solution with the demulcent
in suspension is then introduced into an open vat or vessel provided with means
for mechanically agitating the same. The hides or skins are now introduced
into this solution, which latter is thoroughly agitated for a short period of time.
say for two hours, more or less. The hides or skins are then permitted to remain
at rest in the solution for a comparatively long period of time, say 10 to 12 hours,
more or less, when the solution is again agitated. During the second agitation
the solution is gradually diluted by the addition of fresh water until it contains
no matter in solution or suspension, but is substantially free of the same.

page_text: I am aware that it has been proposed to treat hides or skins for preparing them
for the tanning operation, with a solution of sodium sulphide and water, and that
such will accomplish results provided the nature and character of the skins to
be treated can be accurately ascertained, but in the practice of using the dissolved
sodium sulphide, it has been found that the caustic nature of the sulphide will
act more vigorously on some hides or skins than on others, thus burning the
skins and contracting the grain and depleting the hide or skin of its gelatinous
or glutinous substance.
I am also aware that it has been proposed to use as a depilatory agent a sodium
sulphide solution containing lime, time and arsenic and pipe clay, but in practice
such materials or substances added to said solution are used solely to depilate or
remove the hair and cannot be used for the purpose of preparing the skin for
the tanning operation, since these agents will roughen and harden the grain
of the skin, impoverish the fibre and cause a harshness as well as dryness of the
skin and the skin cannot without further manipulation, be tanned into leather.
By mixing with the sulphide of sodium solution a demulcent such as chalk
or whiting, a liquid compound is provided in the use of which, the caustic nature
of the sulphide is mollified and made far less energetic in its action upon the
gelatinous or glutinous substances of the hides or skins. By reason of its mild
chemical action, the liquid readily softens the gristle, swells the fibre, as well as
effects speedy dissolution of such animal matter as it is desirable to remove.
The skin when treated according to my invention as hereinbefore described, is
ready for the tanning operation and when tanned has a fine, smooth grain and
a firm, plump and mellow feel.
Having now particularly described and ascertained the nature and objects of my
invention and in what manner the same is to be performed, I declare that what
I claim 18:-
1. A liquid compound for treating hides and skins in their raw state to prepare
them for the immediate and subsequent tanning operation, said compound com-
prising a solution of sulphide of sodium and a demulcent such as chalk or
whiting held in suspension in said solution, substantially as and for the purposes
described.
2. A liquid compound or bath for treating hides and skins in their raw state
80 as to swell the fibre, soften the gristle and dissolve animal and refuse matters
therefrom to prepare them for the subsequent tanning operation, said compound
or bath, comprising a solution of sulphide of sodium of required strength to which
is added a demulcent of chalk or whiting, substantially as and for the purposes
described.
3. The improvement in the art of preparing hides or skins for tanning, which
consists in subjecting them to a bath of sodium sulphide and chalk or whiting,
whereby the fibre is swollen, the gristle softened and the animal and refuse
matters dissolved without destruction of the gelatinous and glutinous substances,
substantially as and for the purposes described.
Dated at Philadelphia Pennsylvania this 17th day of November A.D. 1898.
HENRY HOLMES,
Per J. G. Lorrain,
Norfolk House, Norfolk Street, London, W.C.,
Chartered Patent Agent.