IMPROVEMENTS IN DISSOLVING INDIA-RUBBER
Year: 1863

page_text: LETTERS PATENT to Charles Humfrey, of Suffolk Grove, Southwark,
in the County of Surrey, for the Invention of "IMPROVEMENTS IN
DISSOLVING INDIA-RUBBER."
PROVISIONAL SPECIFICATION left by the said Charles Humfrey at the
Office of the Commissioners of Patents, with his Petition, on the 16th
December 1863.
I, CHARLES HUMFREY, of Suffolk Grove, Southwark, in the County of
Surrey, do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN DISSOLVING INDIA-RUBBER," to be as follows:―
The light spirit from petroleums has been employed as a solvent for india-
rubber, but hitherto without success. The india-rubber dissolves therein
with great facility, but on evaporating the solution the deposited gum
remains sticky, its elasticity is destroyed, and in other respects it is unfit for
use.
Now the object of my Invention is so to treat the spirit and the gum, and
to combine them so treated, that I obtain a solution fit for use.
I believe that the following explanation of the cause of the failure which
has hitherto attended all attempts to use petroleum spirit as a solvent for

page_text: india-rubber is correct, but it may be otherwise, and I only state it to render
more easily intelligible the processes I employ, and the principles upon which
my Invention is based. Commercial petroleum spirit appears to me to be
not a true hydrocarbon, but the hydrate of some bydrocarbon, or at any rate
a compound in which water exists combined either chemically or mechanically,
and it is the presence of this water of hydrastation which prevents the gum
from drying and destroys its elasticity, the spirit evaporating and the
water remaining combined, apparently chemically combined, with the gum.
The first essential point then is to obtain anhydrous petroleum spirit, and
this is easily and cheaply effected by either of the following processes --Com-
mercial petroleum spirit of a specific gravity of about 725, free from light
oil, can readily be obtained, and is fit for my purpose. In a convenient closed
vessel, which may be made of wrought iron, and must be fitted with an
agitator, 100 gallons of petroleum spirit are to be mixed with 10 gallons of
concentrated sulphuric acid of a strength not less than 1,840, and brought
into contact by violent agitation. The mixture must then be allowed to rest
a short time, and the acid drawn off by a stop-cock at the bottom of the
vessel. A fresh quantity, about the same of concentrated sulphuric acid, is
then added, and the operation repeated. The spirit, from which nearly all the
acid will settle, must be run with as little exposure as possible to air, especially
to damp air, into another closed vessel also provided with an agitator, and finely
powdered protoxide of lead (ordinary litharge), about 2 or 3 lbs. to every 100
gallons of spirit, must then be added, and the mixture well and repeatedly
agitated. The spirit thus treated is fit for use, and will become bright by a
few hours resting. Or petroleum spirit of the quality above recommended is
introduced into a closed wrought-iron vessel provided with an agitator.
Freshly calcined chloride of calcium in fine powder is added, about 25 lbs.
to every 100 gallons of spirit, and the two are to be brought into intimate
contact by violent and repeated agitation. After settling, the clear spirit must
be drawn off into another similar vessel and therein treated with a fresh dose
of calcined chloride of calcium, and finally must be distilled from calcined
chloride of calcium. This process requires considerable time, several days at
least, and on the whole I prefer the first process.
It will be obvious to any chemist that concentrated sulphuric acid and
calcined chloride of calcium, though the best, are not the only reagents that
can be employed to render the spirit anhydrous. Thus phosphoric acid can be
substituted for sulphuric, and many other substances having a strong affinity
for water for the chloride of calcium, but there are none so cheap and
effectual as those I have recommended. I believe also the quantities above

page_text: recommended are excessive, but the cost is so small and the perfection of the
process so important that I prefer using excessive doses. The sulphuric acid
employed is scarcely injured, only a little weakened, and can be reconcen-
trated at small cost or sold to the manure makers. The chloride of calcium
can be again and again recalcined, and used as often as needed. The
protoxide of lead partially converted into sulphate can be reduced by any
well-known process, and the recovered lead will pay for the litharge. By
contact with water or a watery solution, or exposure to moist air, the spirit
will recover its lost water, and becoming again hydrated will be unfit for use,
it is therefore important to keep it in perfectly dry and closed vessels. The
next essential point is to obtain the india-rubber free from adhering and com-
bined water, and this is readily effected by cutting the gum into thin strips
and exposing them to dry and warm air. Having thus obtained anhydrous
petroleum spirit and anhydrous india-rubber the two together are to be
digested in a closed vessel with agitation, and a solution of any required
strength can be obtained. This solution should not be exposed to the air,
especially to moist air, for the reasons already stated.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Humfrey in the Great Seal Patent Office on the
16th June 1864.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
HUMFREY, of Suffolk Grove, Southwark, in the County of Surrey, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Sixteenth day of December, in the year of our
Lord One thousand eight hundred and sixty-three, in the twenty-seventh year
of Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Charles Humfrey, Her special licence that I, the said Charles Humfrey,
my executors, administrators, and assigns, or such others as I, the said Charles
Humfrey, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
DISSOLVING INDIA-RUBBER," upon the condition (amongst others) that I, the
said Charles Humfrey, my executors or administrators, by an instrument in

page_text: writing under my, or their, or one of their bands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what manner
the same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately after the
date of the said Letters Patent.
NOW KNOW YE, that I, the said Charles Humfrey, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
The light spirit from petroleum has been employed as a solvent for india- 1
rubber, but hitherto without success. The india-rubber dissolves therein
with great facility, but on evaporating the solution the deposited gum
remains sticky, its elasticity is destroyed, and in other respects it is unfit for
use.
Now the object of my Invention is so to treat the spirit and the gum, and 1
to combine them so treated, that I obtain a solution fit for use.
I believe that the following explanation of the cause of the failure which
has hitherto attended all attempts to use petroleum spirit as a solvent for
india-rubber is correct, but it may be otherwise, and I only state it to render
more easily intelligible the processes I employ, and the principles upon which
my Invention is based. Commercial petroleum spirit appears to me to be
not a true hydrocarbon, but the hydrate of some hydrocarbon, or at any rate
a compound in which water exists, combined either chemically or mechanically,
and it is the presence of this water of hydrastation which prevents the gum
from drying and destroys its elasticity, the spirit evaporating and the
water remaining combined, apparently chemically combined, with the gum.
The first essential point then is to obtain anhydrous petroleum spirit, and this
is easily and cheaply effected by either of the following processes :-Com-
mercial petroleum spirit of a specific gravity of about 725, free from light
oil, can readily be obtained, and is fit for my purpose. In a convenient closed
vessel, which may be made of wrought iron, and must be fitted with an
agitator, 100 gallons of petroleum spirit are to be mixed with 10 gallons of
concentrated sulphuric acid of a strength not less than 1840, and brought
into contact by violent agitation. The mixture must then be allowed to rest
a short time, and the acid drawn off by a stop-cock at the bottom of the
vessel. A fresh quantity, about the same of concentrated sulphuric acid, is
then added, and the operation repeated. The spirit, from which nearly all the
acid will settle, must be run with as little exposure as possible to air, especially
to damp air, into another closed vessel also provided with an agitator, and
5

page_text: about 2 or 3 lbs. of protoxide of lead and 1 lb. of peroxide of manganese in
fine powder must then be added to 100 gallons, about, of spirit, and the
mixture must be well and repeatedly agitated. The spirit thus treated is fit
for use, and will become bright by a few hours resting. Or petroleum spirit
of the quality above recommended is introduced into a closed wrought-iron
vessel provided with an agitator. Freshly calcined chloride of calcium in fine
powder is added, about 25 lbs. to every 100 gallons of spirit, and the two
are to be brought into intimate contact by violent and repeated agitation.
After settling, the clear spirit must be drawn off into another similar vessel and
therein treated with a fresh dose of calcined chloride of calcium, and finally must
be distilled from calcined chloride of calcium. This process requires consider-
able time, several days at least, and on the whole I prefer the first process.
It will be obvious to any chemist that concentrated sulphuric acid and
calcined chloride of calcium, though the best, are not the only reagents that
can be employed to render the spirit anhydrous. Thus phosphoric acid can
be substituted for sulphuric, and many other substances having a strong
affinity for water (such as ordinary quicklime freshly calcined) for the
chloride of calcium, but there are none so cheap and effectual as those I
have recommended. I believe also the quantities above recommended are
excessive, but the cost is so small and the perfection of the process so
important that I prefer using excessive doses. The sulphuric acid employed
is scarcely injured, only a little weakened, and can be reconcentrated at small
cost or sold to the manure makers. The chloride of calcium can be again
and again recalcined, and used as often as needed. The protoxide of lead
partially converted into sulphate can be reduced by any well-known process,
and the recovered lead will pay for the litharge. By contact with water
or a watery solution, or exposure to moist air, the spirit will recover its lost
water, and becoming again hydrated will be unfit for use, it is therefore
important to keep it in perfectly dry and closed vessels. The next essential
point is to obtain the india-rubber free from adhering and combined water,
and this is readily effected by cutting the gum into thin strips and exposing
them to dry and warm air. Having thus obtained anhydrous petroleum spirit
and anhydrous india-rubber, the two together are to be digested in a closed
vessel with agitation, and a solution of any required strength can be obtained.
This solution should not be exposed to the air, especially to moist air, for the
reasons already stated.
In this Specification I have used the expression petroleum spirit,"
meaning thereby the spirit obtained from Pennsylvanian and Wallachian

page_text: earth oils, and I consider these the best for my purpose, but the light
spirit obtained from the distillation of coal, shale, and peat can be used.
In witness whereof, I, the said Charles Humfrey, have hereunto set
my hand and seal, this Fifteenth day of June, in the year of our
Lord One thousand eight hundred and sixty-four.
Witness,
ALEX. C. M. PRINCE,
Office for Patents,
4, Trafalgar Square,
Charing Cross.
CHARLES HUMFREY. (L.S.)