Iμ- PROVEMENTS IN EVAPORATING AND BOILING OR CONCENTRATING LIQUIDS, AND IN APPARATUS EMPLOYED THEREIN
Year: 1870

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields,
in the County of Middlesex, Gentleman, for the Invention of "Iμ-
PROVEMENTS IN EVAPORATING AND BOILING OR CONCENTRATING LIQUIDS, AND
IN APPARATUS EMPLOYED THEREIN."-A communication from abroad by
Ꭰ
Sealed the 20th September 1870, and dated the 5th July 1870.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition,
on the 5th July 1870.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
of Middlesex, Gentleman, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN EVAPORATING AND BOLLING OR CONCENTRATING LIQUIDS,
AND IN APPARATUS EMPLOYED THEREIN," a communication to me from abroad
by Jean François Cail, of Paris, in the Empire of France, to be as
follows:-
:-
This Invention relates to an economical mode of utilising caloric for
the purposes of evaporating, boiling, or concentrating liquids, and is more
particularly applicable to the treatment of saccharine juices or syrups
with a view to their manufacture into sugar.

page_text: Liquids have been evaporated by utilising the caloric of the vapour
of evaporation arising from one closed vessel for evaporating liquid
contained in a second vessel at a lower pressure, and again in a third
vessel, but as it has always been considered necessary to employ a
difference in pressure between each vessel equal to about one-fourth
the atmospheric pressure, and to employ, of course, a corresponding
difference of temperature in each vessel, it was consequently found
impracticable to carry out this system with more than three boilers or
closed evaporating vessels in one series.
Now according to this Invention the original caloric may be utilised
an infinite number of times, although in practice from ten to twenty
times will be found amply sufficient. When the caloric is utilised, as
herein-after described, through a series of, say, ten closed vessels or
evaporators an economy of ninety per cent. of fuel will be obtained.
The closed evaporating vessels or boilers may be of various construc-
tions, but it is preferred to make them tubular at the lower part, the
liquid to be evaporated being contained in and passing through the
tubes, whilst the steam for evaporating the same is introduced round
the exteriors of such tubes.
The process of evaporation or boiling is according to this Invention
commenced either at the atmospheric pressure with a decrease of one-
tenth or one-twentieth or less (according to the number of boilers em-
ployed) in each succeeding boiler, or the process may be commenced
at a pressure above that of the atmosphere, and terminated at a pressure
equal to the atmosphere, or, if desired, considerably below it, in which
latter case the two systems of evaporating above and below atmospheric
pressure will be combined in one series of from twenty to forty boilers.
The tubular steam space of the first boiler communicates by a pipe and
suitable stop-cocks, either with the exhaust pipe of an engine or direct
with the boiler or steam generator. From the top of No. 1 evaporating
boiler of the series a pipe conducts the steam arising from the liquid
under evaporation into the tubular steam space of No. 2 boiler, which
discharges its steam arising from the evaporating liquid through another
pipe into the tubular steam space of No. 3 boiler, and so on throughout
the series, the pressure in each decreasing by about one-tenth to one
twentieth of the original pressure, for example, if the pressure in No. 1
boiler be that of the atmosphere, that of No. 2 will be, say, one-tenth
less, that of No. 3 two-tenths less, that of No. 4 three-tenths less, and so

page_text: on. The liquid to be evaporated is introduced by a pump and stop-cocks
into No. 1 boiler and flows through connecting pipes and stop-cocks
into the others of the series, after which the connections are stopped
and the steam is let into No. 1 boiler, when the process commences.
The steam or vapour arising from the last, or nearly the last, of the
series may be conveyed to a condenser. The requisite amount of
vacuum is maintained in each boiler by one or more air pumps and
stop-cocks, and the contents of each boiler may be discharged through
cocks or valves at the bottom thereof.
In some cases, where desirable, the liquid may be pumped out of one
of the boilers after it has undergone a partial concentration, to be treated
in any required manner before its concentration is completed in the
succeeding boilers, and the last two of the series of boilers may be cut
off from the vapours of the preceding ones by suitable valves and em-
ployed separately as concentrators or boilers. Some or all of the boilers
are provided with vacuum guages, guage cocks, and glazed apertures; the
latter for facilitating the inspection of the process and testing the
density of the liquid or syrup under treatment. The water of conden-
sation from the tubular steam spaces is pumped back into the generator
by a pump for that purpose. Another pump is employed for distributing
water or syrup, as the case may be, over the condenser, which commu-
nicates also with an air pump of its own.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 5th January 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN HENRY
JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifth day of July, in the year of
our Lord One thousand eight hundred and seventy, in the thirty-fourth
year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said John Henry Johnson, Her special license
that I, the said John Henry Johnson, my executors, administrators,
and assigns, or such others as I, the said John Henry Johnson, my

page_text: executors, administrators, or 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 EVAPORATING AND BOILING OR CONCENTRATING LIQUIDS, AND IN APPARATUS
EMPLOYED THEREIN," a communication to me from abroad by Jean François
Cail, of Paris, in the Empire of France, upon the condition (amongst
others) that I, the said John Henry Johnson, my executors or adminis-
trators, by an instrument in writing under my hand and scal, 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 John Henry Johnson, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and by
the following statement, reference being had to the accompanying
Drawings and to the letters and figures marked thereon (that is to say):-
The said Invention relates to an economical mode of utilizing caloric
for the purposes of evaporating, boiling, or concentrating liquids, and
is more particularly applicable to the treatment of saccharine, juices, or
syrups with a view to their manufacture into sugar.
Liquids have been evaporated by utilizing the caloric of the vapour
of evaporation arising from one closed vessel for evaporating liquid
contained in a second vessel at a lower pressure, and again in a third
vessel, but as it has always been considered necessary to employ a
difference in pressure between each vessel equal to about one-fourth the
atmospheric pressure, and to employ of course a corresponding difference
of temperature in each vessel, it was consequently found impracticable to
carry out this system with more than three boilers or closed evaporating
vessels in one series.
Now according to this Invention the original caloric may be utilized
an infinite number of times, although in practice from ten to twenty
times will be found amply sufficient. When the caloric is utilized as
herein-after described through a series of, say, 10 closed vessels or
evaporators, an economy of ninety per cent. of fuel will be obtained.
The closed evaporating vessels or boilers may be of various constructions,

page_text: but it is preferred to make them tubular at the lower part, the liquid to
be evaporated being contained in and passing through the tubes, whilst
the steam for evaporating the same is introduced round the exteriors. of
such tubes.
The process of evaporation or boiling is according to this Invention
commenced either at the atmospheric pressure with a decrease of one-
tenth or one-twentieth or less (according to the number of boilers em-
ployed) in each succeeding boiler, or the process may be commenced at a
pressure above that of the atmosphere and terminated at a pressure equal
to the atmosphere, or if desired considerably below it, in which latter case
the two systems of evaporating above and below atmospheric pressure
will be combined in one series of from twenty to forty boilers, the tubular
steam space of the first boiler communicates by a pipe and suitable stop
cocks either with the exhaust pipe of an engine or direct with the boiler
or steam generator. From the top of No. 1 evaporating boiler of the
series a pipe conducts the steam arising from thic liquid under evaporation
into the tubular steam space of No. 2 boiler, which discharges its steam
arising from the evaporating liquid through another pipo into the
tubular steam space of No. 3 boiler, and so on throughout the series,
the pressure in each decreasing by about one-tenth to one-twentieth of
the original pressure, for example, if the pressure in No. 1 boiler be
that of the atmosphere, that of No. 2 will be, say, one-tenth less, that
of No. 3 two-tenths less, that of No. 4 three-tenths less, and so on.
The liquid to be evaporated is introduced by a pump and stop-cocks into.
No. 1 boiler, and flows through connecting pipes and stop-cocks into the
others.of the series, after which the connections are stopped and the steam.
is let into No. 1 boiler, when the process commences.. The steam or vapour
arising from the last or nearly the last of the series may be conveyed to.
a condenser. The requisite amount of vacuum is maintained in each
boiler by one or more air pumps and stop-cocks, and the contents of each
boiler may be discharged through cocks or valves at the bottom thereof.
In some cases where desirable the liquid may be pumped out of one of
the boilers after it has undergone a partial concentration, to be treated in
any required manner before its concentration is completed in the succeeding
boilers, and the last two of the series of boilers may be cut off from the
vapours of the preceding ones by suitable valves and employed separately
as concentrators or boilers. Some or all of the boilers are provided with
vacuum gauges, gauge cocks, and glazed apertures, the latter for facilitating

page_text: the inspection of the process, and testing the density of the liquid or syrup
under treatment. The water of condensation from the tubular steam spaces
is pumped back into the generator by a pump for that purpose. Another
pump is employed for distributing water or syrup, as the case may be,
over the condenser which communicates also with an air pump of its own.
The explanatory Drawings hereunto annexed shew a series of boilers
working at pressures below that of the atmosphere, and I shall also
describe without reference to Drawings the modifications necessary in
order to construct apparatus to work at pressures exceeding that of the
atmosphere.
The following description exemplifies the application of the Invention
and apparatus to the evaporation and final concentration of the juices and
syrups of cane or beet root, that is to say, to the manufacture and refining
of sugar, both at pressures above and below that of the atmosphere, but
it should be understood that it is simply an example.
I claim not merely its application to the above purposes, but also to
the concentration of the juices and syrups of glucose and all vegetable
juices and essences of saline waters, whether natural, animal, or artificial,
such as, for example, sea water, vichy, or other mineral water, urine, various
solutions from chemical manufactories, ascetic vinegar of distilleries, and
in fact for any manufacture where large quantities of water are
required to be evaporated.
As herein-before stated it has been discovered possible to commercially
utilize the caloric about twenty times for each atmosphere. The
apparatus shewn in the Drawings is, however, designed to utilize it only
ten times since the Invention will be probably be chiefly applied in this
manner. In fact about two pounds of steam introduced into the tubular
apparatus of a primary boiler when utilized ten times effects, with the
exception of some losses, a saving of ninety per cent. over the method
of a single use of the steam, that is to say, for an evaporation which
would have cost two hundredweight of coal in a single-acting apparatus
only one-fifth of an hundredweight will be consumed, making a saving
of one and four-fifths of an hundredweight. If we assume ten boilers
more added in order to utilize the caloric twenty times, the cost
of fuel will be reduced one half, or instead of being one-fifth it will be
about one-tenth of an hundredweight. In the majority of cases, that is,
wherever coal is not too dear, it will be preferable to adopt the former
number of boilers on account of the expence of obtaining and erecting

page_text: the additional ten boilers necessary in order to secure the further saving.
For this reason I have simply shewn on the Drawings an apparatus
adapted to the use of the vapour ten times; it would be, moreover,
uscless to shew a greater number, since in order to construct an apparatus.
capable of effecting it, all that is required is to add boilers to the
evaporating apparatus shewn, whilst on the other hand, the number of
boilers may be reduced if it be found desirable to limit the uses to a less
number; the differences in the pressure between any two contiguous.
boilers will of course decrease or be augmented according as boilers are
added or omitted, and they will be, according to the number of boilers
employed, twentieths, fifteenths, or fifths of an atmosphere in lieu of
being tenths, as in the example following.
In the Drawing referred to Figure 1 represents a range of evaporating
boilers and condensers, some of which evaporators are shewn in section,
and Figure 2 is an enlarged elevation of a portion of one of the boilers
shewing the external fittings.. C¹ to C¹ are evaporating boilers each
provided with a tubular box, and supported by special columns D carrying
discharge pipes; R' is a cock admitting of the escape from the engine
into the atmosphere; R² is a cock for the introduction of the escaped
steam of the engine into the tubular box of the boiler C₁; T¹ to T are
tubes placed on the upper part of each boiler to conduct the vapour of
evaporation into the tubular box of the next boiler (see the section of
the boiler C). T is a pipe which conducts the vapour of evaporation
from either of the boilers C C°, and C, (the two latter being supposed
to be disposed one behind the other, so that only one in fact can be seen
on the Drawing) to the condenser by means of the valves S¹, S², S³, S*,
S. R³ is a cock which enables the whole or a portion of the escaped
vapours to be conducted to the boilers for the final concentration through
the cocks R' and R. Re is a cock to conduct steam direct for the
service of the apparatus in certain cases. R is a cock to admit the
juice into the first boiler. R³ arc cocks for the conveyance of juice
from one boiler to the other. R³ is a cock designed to place the third
boiler and the pump P in communication when it is required to subject
the liquid to be evaporated to any operation before completing the
concentration, which arrangement may be also applied to any other
boiler. R is a cock for the return of the juice to the fourth boiler,
after it has undergone the operation herein-before referred to, the return.
of the juice is effected according to circumstances, either by the partial
vacuum in the boiler or by a force pump, when working under pressure.

page_text: rare cocks or valves applied to the boilers. E are test glasses to try the
density of the juice, and which may be placed on other boilers, and even
on all, according to circumstances and the exigencies of the case.
M are
proof sticks for the boilers set apart for the final concentration, which
when the apparatus is applied to other manufactures may be replaced
by test glasses. L glazed apertures disposed on the boilers for the
purpose of inspecting the interior; I, vacuum gauges which may be of
any suitable description; P" is a pump for the purpose of drawing off
through the cock R", the liquid to be evaporated along the pipe J' and
forcing it back into the first boiler; P is a suction and force pump for
emptying the third boiler and directing the liquid into the apparatus where
it may be subjected to any required operation; P" is a suction and force
pump for the purpose of sprinkling the condenser with either water or
juice, according to circumstances by means of the three way cocks O, O;
P is a feed pump taking the condensed water in the tubular box of the
first boiler, in order to force it back into the generator; P¹ to P³ are air
pumps taking the condensed water of the boilers C to C10; P1 is the
air pump of the condenser; A are pipes for placing the boilers and
condenser in communication with the air pumps and the feed pump of the
first boiler; G is a gutter for carrying off the water from the air pumps;
J' is the tube for the arrival of the juice; J, J³, are tubes for con-
ducting under the suction of the pump, P, the water or juice which
is to be distributed over the condenser; J' is a tube for the forcing back
of water or juice over the condenser.
The apparatus operates in the following manner :-The pumps having
been set in motion, the liquid to be evaporated is directed into the
boiler C¹ by means of the pump P" and the cock R', the cocks R³ are
opened and the feeding is continued until the heating surfaces of all the
feeding is continued until the heating surfaces of all the boilers are
sufficiently covered. In the case of the manufacture of sugar, the first
eight boilers only may be supplied to commence with, and the vapour
from the eighth may be conducted directly on to the condenser through
the pipe T, thus reserving the pair of boilers C and C₁ for the final
concentration. In the example shewn, the two latter boilers are made
of special dimensions for this operation to which they are destined,
but in other manufactures it is in general desirable to feed at the com-
mencement the whole of the boilers, to place C° and C1 in the same line
as the others, and so to arrange them as that C shall be heated by the
vapours at C³, and C10 by those of C. As soon as the supply is completed

page_text: the communicating cocks R³ are closed, as also the suction cock R" and
the inlet cock R. The first boiler is then heated, either by the escaped
steam by opening the cock R³ and closing the cock R¹, or by steam
direct by leaving the cock R¹ open and opening the cock R. The
liquid contained in the boiler C¹ enters into a state of ebullition and the
vapour proceeding therefrom is drawn into the tubular box of the boiler C³,
through the pipe T₁ by means of the air pump P', whilst the condensed
steam in the tubular box of C¹ is taken by the feed pump P" in order to
be forced back into the generator. The liquid from C³ in its turn enters
into a state of ebullition, the vapour of evaporation is drawn into the
tubular box C³ through the pipe T₁ by means of the air pump P³ whilst
the condensed steam in the tubular box C² is carried off by the air
pump P¹, which discharges it into the gutter G, and so on in succession,
until the last boiler, the vapour of evaporation of which is drawn off
through the condenser by the air pump P10
In order to operate with advantage it is desirable to heat the boiler C
with steam sufficiently expanded to enable it to work under a pressure
about equal to that of the atmosphere, which I represent by (1), and if
the air pumps work properly this pressure will be seen to diminish from
the first to the last boiler, by about one-tenth of an atmosphere, say,
0.076 of mercury between them; and after the apparatus has been
working a few moments the following approximate pressures will be
established:-

page_text: If the boilers C and C in lieu of both being heated by the vapour
of C³ were heated, C' by CB and C by Cº, the reduction of pressure in
C¹o would be one-tenth more, say, 0.684 under the declining pressures
approximately indicated in the above table, the evaporation continues
and the level of the liquid in the boilers is prevented from diminishing
by feeding C¹, by means of the pump P" and the cock R', and then by
opening successively the communication cocks R³. When the liquid to
be evaporated is to be subjected to any treatment before the complete
concentration it is discharged from the boiler in which it has attained
the desired density by the arrangement indicated with reference to the
boiler C³ videlicit by means of the apparatus R³ and P¹³.
In the manufacture or refining of sugar it is desirable in the final
concentration in order to obtain a fine crystallization to operate on
tolerably large masses at one time, and consequently a baking of this
description continues for some considerable time; for this reason the
boilers C and C" are shewn larger than the others, and in order to
facilitate the discharge of the thick masses these boilers are provided
with valves in lieu of cocks, and the tubes are made of greater diameter.
Two boilers are reserved for this operation in order to admit of one being
commenced when the other is completed, and also to enable syrups from
second and third discharges to be there treated. Notwithstanding these
dimensions the boilers C° and C¹ may be applied to the purposes of
evaporation at such times when there are no bakings to be effected; and
they are so disposed as to enable them to be heated either separately or
simultaneously by the vapour of the boiler C³. In order to obtain these
results the operation is carried out in the following manner :-If it be
required to operate with the boiler Cº, leaving the boiler C at rest, the
valves S¹ and S³ are opened, and the valves S³, S³, and S* closed, and the
suction of the condenser is effected on this boiler through the pipo To.
If, on the contrary, it is desired to operate with C, leaving Cº at rest, the
valves S and S' are opened, and the valves S1, S2, and S³ closed, and the
suction is performed on C". Or when it is desired to work both C° and
C¹º simultaneously the valve S' is closed, and the valves S', S³, S', and S³
are opened, care being taken to regulate the opening of the valves S¹
and S³, so that the vapour of evaporation from Cs may be equally
distributed over C' and C. If it be required to leave both C and C™
at rest the valves S¹, 8³, 8', and S are closed, the valve S2 being left
open

page_text: Having now described the apparatus designed to work at pressures
below that of the atmosphere, a very slight additional description will be
necessary to explain the apparatus which works at higher pressures, and
which, if it be required to multiply the uses for the heat, may greatly
exceed the atmospheric pressure, provided always that the boilers be
constructed of sufficient strength. This apparatus differs but little from
that herein-before described, since all that is required in order to ensuro
suitable pressures in the tubular boxes and on the liquids to be
evaporated is to employ in the first boiler steam sufficiently expanded to
substitute for the air pumps feed pumps properly regulated for this
purpose, or apparatus for returning water known as float regulators, and
to allow the vapour of evaporation from the last boiler to escape into the
atmosphere. The starting of the apparatus and its mode of working are
the same, as well as the differences of pressure between any two vessels.
Thus, assume that it is desired to work at a pressure of one atmosphere
more than that of the surrounding atmosphere, and let the latter be
represented by (1) as in the preceding example, then eleven effects may
be obtained in eleven boilers working under the following pressures :—
The vapour from the last boiler escaping into the atmosphere. With this
pressure of two atmospheres even twenty-one effects may be obtained
and the difference between any two boilers will be but one-twentieth of

page_text: an atmosphere. In fact, a series consisting of any number of boilers
may be combined, the first boilers working at high pressures and modified
for this purpose, and the boilers forming the latter portion of the series
provided with air pumps as shewn in the Drawing and working at
pressures below that of the atmosphere. In this case if there be
employed in the first boiler steam sufficiently expanded in order to
maintain there a pressure equal to one atmosphere above the atmospheric
pressure, the evaporating apparatus thus constituted will work at
pressures constantly decreasing, but which in the first half of the series
of the boilers will exceed the pressure of the atmosphere whilst they
will be equal to and below that pressure in the second half of the series.
It will be understood that this example applies to a number of boilers
either greater or less than ten. Thus in lieu of producing a pressure of
one atmosphere above that of the surrounding air in the first boiler, a
lower pressure may be commenced with, and then the number of boilers
working under high pressures will be less than that of the boilers
working at low pressures. If, however, the products to be obtained by
evaporation are not liable to be deteriorated by a high temperature, a
greater pressure may be produced in the first boiler, and the number of
times the vapour is employed thus augmented. In this case the number
of boilers working under pressures exceeding that of the atmosphere
will be greater than that of the boilers working at lower pressures.
This novel combination, to which I lay claim, and which consists of an
evaporating apparatus in which the first boilers of a series work under
pressures exceeding that of the atmosphere while the following ones
work at pressures below that of the atmosphere, is particularly recom-
mended as being highly advantageous on account of the rapid circulation
thus imparted to the vapour.
The apparatus herein-before described appear to be the most suitable to
carry out this Invention, but the same result may be arrived at with
different forms and other arrangements of heating surface, I do not
therefore confine myself to the apparatus herein-before described as an
example, and I reserve to myself the right to utilize the caloric by
worms, double bottoms, and other suitable arrangements, as also to
dispose the apparatus horizontally and to make them of a rectangular :
or spheroidal form.
Any portions of the evaporating apparatus hercin-before described
may be modified or dispensed with or additions may be made thereto,

page_text: according to the special requirements of the manufacture or the arrange-
ments of the works. Thus in some special cases where the expanded
steam of a number of engines is employed or the return or waste steam
from any apparatus whatever, without having relatively much evapo-
ration to perform, the initial heat might be employed a less number of
times either at low pressures as in this case, or at pressures exceeding
that of the atmosphere.
In the evaporating apparatus illustrated by the Drawings, each boiler
is provided with an air pump operating independently, which draws and
forces the water which is condensed in the tubular part of the apparatus,
but one air pump alone may be employed, particularly in those cases
where the heat from the primary steam is not employed many times,
and this Invention could be equally carried out by the use of a single
air pump of sufficient power, care being taken to provide the tubular
portion of each boiler with a special conduit for the draught and
discharge of its water leading to the air pump which would then bo
disposed next to the condenser. The same observation applies to the
feed pumps with which the boilers working at pressures above that of
the atmosphere are provided.
In order to prevent confusing the Drawing, I have omitted to shew
the circulating pipes for the juice in the tubes and the plates for the
circulation of vapour in the tubular box, with which appendages the
treble action apparatus of the inventor is usually provided, and which
may be also advantageously applied to the new apparatus. In the case
of the treatment of liquids which are liable to bo. carried away during
ebullition, safety vessels may be placed either above each boiler or
between the boilers.
The peculiar construction of evaporating condenser illustrated on the
Drawings is preferred, since it gives the most useful effect of any appa-
ratus of this description, more especially if, as stated, the condensation
of the vapour of the last boiler be effected by sprinkling the condenser
with the liquid to be evaporated, and since cither in this case or when
the warm water of condensation which necessarily leaves it or the
water from any of the air pumps is poured over it again in streamlets
the necessary expenses of procuring cold water, which is indispensable
in the case of injection condensers, are entirely saved, whilst on the
contrary a large quantity of warm water is placed at the disposal of
manufacturers for use for various purposes, which would enable works

page_text: to be established in localities where there is a deficiency in water supply.
This evaporating condenser may however be replaced by an immersion
condenser which also gives a useful effect either by heating the liquid
to be evaporated or by heating water, which in consequence of its purity
may be applied to a great number of purposes, or even an injection
condenser may be substituted therefor.
The dispensing with certain parts and the modifications and additions
may all be useful according to the different circumstances of the place
where this Invention and these apparatus are applied, but they neither
alter the nature of the apparatus nor their general object of utilizing
an unlimited number of times the heat necessary for a primary evapo-
ration when the differences in the decrease of pressure are observed,
which the Inventor was the first to discover to be sufficient and
practicable and to experimentally determine.
Having now described and particularly ascertained the nature of the
said Invention and the manner in which the same is or may be used or
carried into effect, I would observe in conclusion that what I consider
to be novel and original and therefore claim as the Invention secured to
me by the herein-before in part recited Letters Patent is, the improved
system or mode of and apparatus for economising heat in the process of
evaporation substantially as herein-before described and illustrated by the
Drawings annexed.
In witness whereof, I, the said John Henry Johnson, have to this
my Specification set my hand and seal, the Fourth day of
January One thousand eight hundred and seventy-one.