An Improved Mixture for Use in Apparatus for Producing Cold.
Year: 1889

page_text: Date of Application, 7th Aug., 1889-Accepted, 28th Sept., 1889
COMPLETE DIEUIFICA
An Improved Mixture for Use in Apparatus for Producing Cold.
I JAMES YATE JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of this Invention (which has been com-
nunicated from abroad by La Compagnie Industrielle des Procédés Raoul Pictet
of Paris in the Republic of France) and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
tatement:-
According to this lnvention a mixture containing Carbonic Acid and Sulphurous
Acid in certain proportions is substituted for the liquid sulphurous acid, SO usually
employed in apparatus for producing cold. Some difficulty has been experienced in
ascertaining the exact quantity of carbonic acid to be dissolved in the sulphurous
acid. In determining this quantity it is necessary to take into consideration at the
same time
(1) the lowering of the boiling point of the mixture and (2) the dynamic or
mechanical action or work done by the apparatus employed to liquefy the mixture.
The annexed diagrams show the limits within which the composition of the mixture
may vary in order to obtain at the same time a good effect and the most advantageous
temperature possible. In these diagrams the curves in figure 1 show the proportion
between the temperature and the pressure of the different mixtures. The diagram
figure 2 represents the work necessary to produce the liquefaction of the gaseous
15 and compressed
mixture CO SO', the vapours being assumed to be drawn in at
to +30 degrees centigrade. The figures on the left hand side in figure 1 represent
atmospheres and the figures at the bottom degrees centigrade.
―
In figure 1 the diagram 1 represents the variations in temperature and pressure
with the employment of sulphurous acid the diagram 4 representing the variations
with sulphurous acid saturated with carbonic acid and the diagrams 2 and 3
representing the variations of temperature and pressure with sulphurous acid
impregnated with intermediate proportions of carbonic acid. On comparing these
diagrams it is found that the more the proportion of carbonic acid dissolved in the
mixture increases the more the temperature of the mixture diminishes or falls for a
given amount of pressure.
-
Thus these diagrams show that with pure sulphurous acid, diagram 1, a pressure of
one atmosphere which is sufficient to bring it to the temperature of ebullition corre-
sponds with a temperature of 12 degrees centigrade (as indicated at H) but when
the sulphurous acid is saturated with anhydrous carbonic acid (diagram 4) the point K
at which ebullition takes place is about 30 degrees centigrade. From an
examination of these curves it may be concluded that for a given volume of vapour
the amount of cold obtained with pure sulphurous acid is equal to about two thirds of
that obtained with sulphurous acid saturated with carbonic acid. The pressure at L
of the sulphurous acid at 15 degrees centigrade is about 0.9 atmospheres bui at M
the pressure of the saturated acid at the same temperature is about 1.4.
-
On referring to figure 2 which represents the work required to liquify the gaseous
mixture it will be seen that the dynamic action does not follow the same law. The
area D D II E D represents the work necessary for the liquefaction of pure
sulphurous acid. The area A A¹ F¹ F E A represents the work necessary for the
liquefaction of saturated sulphurous acid and the areas B E G G' B' B and CEHH'
CC represent the work necessary for the liquefaction of sulphurous acid impregnated
with carbonic acid to intermediate degrees.
It will be found on referring to this diagram that the area representing the work
required for the compression of pure sulphurous acid is not two thirds of the area
indicating the work absorbed by the liquefaction of sulphurous acid saturated with
arhonic sid

page_text: It appears that the work absorbed increases with the quantity of carbonic acid
dissolved but the difference in the two amounts of work is relatively considerable.
The saving of work by the employment of the saturated liquid is about ten per cent. of
the work necessary for the compression and the sulphurous acid saturated with
carbonic acid is consequently employed according to this invention for the following
reasons,
1. For a given quantity of cold to he produced a smaller compressing pump is
enabled to be employed.
2. At the same time the amount of work necessary to produce cold is diminished.
The mixture of sulphurous and carbonic acid is obtained by causing gaseous carbonic
acid to bubble through liquid sulphurous acid at a low temperature. This operation
must be stopped when the pressure of the saturated liquid is greater for a given
temperature than its normal pressure corresponding to the curve marked 4 in
figure 1.
In practice the refrigerating machine or apparatus is started with pure sulphurous
acid and then the carbonic acid is slowly or gradually introduced into the circulation
until saturation results.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A mixture for use in refrigerating or cold producing machines consisting of
sulphurous acid saturated with carbonic acid this saturation being effected either
before or after the apparatus is put in motion in the manner and for the purpose
substantially as herein before described.
Dated this 7th day of August 1889.