Process and Apparatus for Producing Gaseous Mixtures, mainly Formic Aldehyde, for Disinfecting Purposes.
Year: 1896

page_text: Date of Application, 27th May, 1896-Accepted, 11th July, 1896
COMPLETE SPECIFICATION.
Process and Apparatus for Producing Gaseous Mixtures, mainly
Formic Aldehyde, for Disinfecting Purposes.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, do hereby
declare the nature of this invention (which has been communicated to me from
abroad by The Société Anonyme de l'Institut Raoul Pictet of Fribourg,
Switzerland), 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 process and apparatus for producing gaseous
mixtures, mainly pure formic aldehyde, for disinfecting purposes.
Up to the present time the formic aldehyde employed in a gaseous state for
disinfecting has been impure and mixed with toxic gases such as for example
carbonic oxide. It has been proposed to produce formic aldehyde by heating
trioxymethylene, but the concentration of the aldehyde so obtained led to the
polymerisation of a large proportion of the product.
By this invention gaseous mixtures containing pure formic aldehyde are easily
obtained, very rapid working is ensured, no danger is incurred, and mixture in
strictly measured mixtured quantities can be obtained.
The process consists in causing a current of hot gases to pass over trioxy-
methylene or other solid polymeride of formic aldehyde, these gases in their
passage becoming charged with pure formic aldehyde.
The gases employed may be air or any antiseptic or other gas.
The apparatus, a vertical section of which is shown in Figure 1 of the annexed
drawing, is particularly suitable for carrying out this process.
It consists of an outer cylindrical casing A, the lower portion of which is
pierced with a hole a and in the top of which are arranged a certain number of
openings a'.
The cylinder A. is closed with a cover a² in which a thermometer a is fixed in
any suitable manner.
This cylinder is placed upon a fire-box B of any suitable type.
Inside the cylinder A a worm C is arranged, it is connected at the top by means
of the pipe c to a tube c' which is provided with a cock c².
This worm surrounds a receiver D which can be opened in the middle as
shown.
At the bottom of the receiver is a tube d closed at the lower end, into which the
worm Copens.
A conical shell d' in which are suitable holes is inserted between the receiver D
and the tube d, its under part enters the tube d and its head extends into the
receiver D. At the top of the receiver is a tube d³ the upper portion of which is
closed by a screw cap d³ which can be removed, and which rests upon a ring or
collar d placed on the cover a².
A second worm E similar to the first surrounds the tube d to the lower portion
of which it is attached.
The other end is connected to the tube e fixed upon the cylinder A.
These worms are as is shewn attached to the several pieces by means of screw
unions or otherwise.
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page_text: The apparatus works in the following manner
The vessel D is charged with trioxymethylene or other polymeride of formic
aldehyde; the fire or burner in B is lighted, and then a current of gas or other
antiseptic kept under pressure, or directly compressed by any suitable means is
introduced by the pipe el. This current becomes heated by passing through the
worm C, from top to bottom and passes out by the holes arranged in the shell d', it
passes through the material becomes charged with formic aldehyde and passes out
of the receiver by the worm E in which the powder mechanically carried forward
by the current is transformed.
The gas charged with pure formic aldehyde passes out of the apparatus by the
tube e and flows to the spot to be disinfected.
Of course the apparatus could be worked inversely by suction through the
tube e.
In some cases a certain quantity of humidity is necessary to obtain good
disinfection by means of formic aldehyde.
For this purpose a certain quantity of steam may be admitted to the place to be
disinfected when the moisture of the air is insufficient.
The steam may be introduced at the same time as the formic aldehyde by slightly
modifying the apparatus as shewn in Figure 2.
The upper portion of the receiver instead of being screwed upon the lower
portion, is simply fitted to it. There is placed between the two portions a ring of
asbestos, or other material the whole is secured by means of bolts or locking
screws.
Also the upper portion carries two tubes, one at the side for the passage of a
copper case for receiving a thermometer, the other central, as is the case in
Figure 1, but the screw cap which closes the upper portion gives passage to a tube
provided with a cock and a glazed sight hole. This tube communicates with a
reservoir or vessel, the neck of which is closed with a screw cap. A metallic tube
starting from the cap of the vessel containing the trioxymethylene opens into the
upper part of the reservoir placed on the said vessel.
This reservoir contains water, which may be caused to flow in a continuous
manner into the lower vessel.
F, Figure 2, is the upper vessel, f its central tube which passes through the
cap da cock, upon the tube f, a sight hole.
Gis a tube connecting the upper portions of the two vessels, II is the thermometer,
H¹ its copper case.
Instead of simultaneously employing the solid polymerides of formic aldehyde,
such as trioxymethylene and water, a solution of formic aldehyde may be introduced
into the apparatus being placed in the vessel F.
The concentration of the solution will be increased according to circumstances
until the limit at which trioxymethylene will be itself employed; under these
conditions the heat will have for first effect to volatilize the water and carry off a
portion of the formic aldehyde, then the trioxymethylene will be disassociated in
its turo.
The operation is therefore in this case to obtain in the apparatus itself the
rioxymethylene, or rather the indefinite series of polymerides of formic aldehyde.
In all cases, a suitable current of air is caused to pass into the apparatus.
The details of construction of the apparatus may be varied.
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 :-
1. The process for the production of gaseous mixtures, mainly pure formic
aldehyde, which consists in causing a current of antiseptic or other hot gates to
pass over tri-xymethylene, or other solid polymeride of formic aldehyde.
2. The apparatus for producing the said gaseous mixtures, substantially as
described and shewn in Figure 1 of the annexed drawing.

page_text: 3. The apparatus modified as illustrated by Figure 2, providing for the production
of steam during the operation and the employment of a solution of formic
aldehyde.
SYDNEY PITT.