Improvements in the Purification of Acetylene, and in Apparatus therefor.
Year: 1896

page_text: Date of Application (in United Kingdom), 17th Aug., 1896
Complete Specification Left, 17th Aug., 1896-Accepted, 28th Nov., 1896
COMPLETE SPECIFICATION.
Improvements in the Purification of Acetylene, and in Apparatus
therefor.
I RAOUL PIERRE. PICTET of Geneva Switzerland 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 improvements in the purification of acetylene
and apparatus therefor.
Acetylene gas formed by the action of water on calcium carbide, or "carbite,"
contains a number of impurities whose action is very injurious. Ammonia
hydrogen, sulphuretted, arseniuretted and carburetted hydrogen, and carbonio
oxide are found in varying proportions in acetylene according to the nature
of the materials employed in the electric furnaces for the manufacture of the
calcium carbide.
These impurities give to the acetylene special characteristics: impure acetylene
attacks nearly all common metals, specially copper, forming with these bodies
compounds of which some are detonating, aud the illumating power of the gas is
seriously diminished by the presence of these impurities. Impure acetylene burns
with a flame surrounded with a purple halo, which is only slightly luminous: this
halo disappears when the acetylene is pure. It is therefore important to purify the
gas by simple and inexpensive processes so as to avoid the above drawbacks and to
raise the illuminating power to a maximum.
In the specification accompanying another application for a patent of even date
with the present application I have described a method of manufacturing acetylene
which produces the gas in an already high state of purity. In order to obtain
complete purification I accordingly prefer to start with gas made by my new
process but it is obvious that 1 can also apply my process of purification, described
below, to acetyleno obtained by any other process.
My process consists in.
(1.) Making the gas bubble through a concentrated solution of calcium chloride
cooled down to a convenient temperature between -20° C. and 40° C.
(2.) Passing the gas through a solution of sulphuric acid of about 40 per cent.
concentration cooled down to a convenient temperature between -20° C. and
-60° C.
(3.) Washing the gas with a solution of lead salts at the ordinary temperature.
(4.) Drying the gas by passing it over crystallized calcium chloride to complete
the purification.
Chloride of calcium acts like a sponge for all the impurities of acetylene of which

page_text: it removes especially the most dangerous, ammonia and its derivatives; and if the
gas is split up into very small bubbles all traces of ammonia and water vapour
disappear.
As is well known chemical reactions entirely cease at low temperatures and
there is a selective order in which the reactions progressively diminish. Now the
action of sulphuric acid on acetylene ceases almost completely at 20° C. It is
therefore possible to take solutions of sulphuric acid and water which is still liquid
at temperatures below-20° C. and only solidifying towards - 70° C. or -80° C.
through which to bubble the acetylene in order to fix physically and chemically the
impurities whose point of reaction with sulphuric acid is lower on the scale of
temperatures than that of pure acetylene.
Owing to this simultaneous action of chemical compounds such as solutions of
calcium chloride and sulphuric acid and of low temperatures the acetylone can be
completely freed from the dangerous impurities which it contains.
Analogous results may be obtained with solutions of other chlorides of alkaline
metals sodium, magnesium potassium chlorides &c. and with other non volatile
acids such as for example phosphoric acid.
By washing with lead salts and drying with anhydrous chloride of calcium,
complete purification of the acetylene may be obtained.
In the drawing annexed I have shown for the sake of example an apparatus by
which my purifying process can be practically carried into effect.
In this drawing A A' are vats in which I set up the circulation of some
refrigerating liquid B B B are three vats the first two being supported on
girders a a in the vats A A' and being surrounded with the refrigerating
liquid, bb 6 are vertical pipes which conduct the acetylene to the bottom of the
vats B B B. CC'C' are flanged plates pierced with holes so as to divide up the
gas and to obtain a most intimate contact with the solutions.
D is a pipe for the entrance of the refrigerating liquid, D' a pipe by which it
passes from the vat A to the vat A¹ and D' the exit pipe. E is a column containing
crystallised calcium chloride. 1, 2, 3, 4, 5 are pipes for conducting the gas.
The acetylene to be purified is delivered by the pipes 1 and b at the bottom of
the vat B which contains a solution of calcium chloride which is kept at the desired
temperature above -40° C. The gas after having traversed the solution by passing
up through the holes pierced in the plates C is led by the pipes 2 and to the
bottom of the vat B' containing the solution of sulphuric acid at a low temperature
it then rises in this vat through the holes in the plates C' and arrives by the pipes 3
and at the bottom of the vat B. This vat contains a solution of lead salts at
the normal temperature. The acetylene traverses this solution passing through the
holes in the plates C and enters the pipe 4 by which it arrives at the bottom of
the column E. The purification of the gas is completed while it is rising in this
column over the crystallized calcium chloride contained therein and it is then
conducted by the pipe 5 to a gasometer.
It is unnecessary to add that I have described this apparatus snerely for the sake
of example and I reserve to myself the right of adopting any arrangement suitable
for carrying out the purifying process which I have desoribed.
In certain cases I could employ in lieu of the exterior vats containing the
refrigerating liquid, a worm placed in the solutions themselves through which some
refrigerating liquid circulates or I could combine these two arrangements. Also
there need be no communicationD between the refrigerating baths when it is desired
to maintain different temperatures in the vats A and A'.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The process for the purification of acetylene which consists in bubbling the gas
through a concentrated solution of calcium chloride, then through sulphuric acid of
about 40 per cent. concentration, these two solutions being kept at suitable

page_text: temperatures then-if necessary-washing it in a solution of lead salts at the
ordinary temperature and lastly drying it by contact with crystallised onloium
chloride substantially as described.
Dated this 17th day of A vonat 1008
CARPMAEL & Co.,
Agents for the Applicant.