IMPROVEMENTS IN THE MANUFACTURE OF PHOSPHATES OF LIME, AND IN APPARATUS EMPLOYED THEREIN.
Year: 1871

page_text: LETTERS PATENT to Campbell Morfit, of Baltimore, Maryland, in the
United States of America, but at present of 35, Southampton
Buildings, in the County of Middlesex, for the Invention of
"IMPROVEMENTS IN THE MANUFACTURE OF PHOSPHATES OF LIME, AND IN
APPARATUS EMPLOYED THEREIN.
"
Sealed the 26th September 1871, and dated the 13th April 1871.
PROVISIONAL SPECIFICATION left by the said Campbell Morfit at the
Office of the Commissioners of Patents, with his Petition, on the
13th April 1871.
I, CAMPBELL MORFIT, of Baltimore, Maryland, in the United States
of America, but at present of 35, Southampton Buildings, in the County
of Middlesex, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF PHOSPHATES OF LIME, AND IN APPA-
RATUS EMPLOYED THEREIN," to be as follows:-
The Invention relates to the treatment of bones, bone ash, bone black,
mally by certain

page_text: The mode of carrying my Invention into effect is as follows:-The
raw phosphate material is reduced first to powder and then put into a
vat. This vat is of flag stone or other material which will resist the
action of acid. As it is to serve the part of a digester it has a suitable
cover hung over pulleys by chains, and furthermore is enclosed by a wall
so built and covered as to leave an intervening space as a hot air
chamber. Through this chamber and encircling the exterior of the vat
is a series of iron tubes for the passage of steam as the means of heating.
Hydrochloric acid is next added to the powdered material in this vat
to dissolve out all of the carbonate of lime, phosphate of lime, and
phosphate of magnesia, and after the effervescence has subsided the cover
is lowered and steam passed through the tubes. The heating and
digestion is then to be continued judiciously as to time and temperature,
so that as little as possible of fluoride of calcium, aluminium, and iron
compounds may be taken up with the phosphates and carbonato.
Assuming that hydrochloric acid of specific gravity 1-17 is employed,
then about 2.13 pounds will be required for every pound of carbonate of
lime and in addition about 1-40 pounds for every pound of phosphates,
lime, and magnesia, which the raw material under treatment may contain.
When all the carbonate and phosphates have been taken up in solution
by the acid the digestion is finished and the whole must be left to repose.
The clear upper liquor is then to be drawn off from the settlings beneath
into a separato vessel designated the precipitation vat. This vat may be
of wood covered with protecting paint or hard pitch and must have
dipping into it several steam pipes as a means of heating its contents
when necessary. The settlings or insoluble residue are next to be washed
three several times with as many relays of fresh water, and after each
settling, as before, the wash water is to be drawn off into the precipi-
tation vat containing the previous stronger liquor. The settlings being
now exhausted and cleansed are to be thrown out as waste. The liquor
in the precipitation vat is an hydrochloric solution of all the phosphates
of the original or raw phosphate material. It contains also the whole of
the carbonate of lime and some of the alumina and oxide of iron as
chlorides. The next step is to separate the former from the latter in a
state wholly or nearly pure. This is done by heating the liquor by
means of steam currents to from 200° to 212° Fahrenheit and adding

page_text: during the agitation and high temperature thus promoted that kind
of carbonate of lime known as whiting. This latter must be in a
fine powder and added through a sieve for its better distribution
over the entire surface of the liquor. It must also be added by degrees
and always at such intervals between the doses as will allow the
effervescence from a previous portion to subside before the succeeding
one is sifted in. This treatment with whiting leaves the carbonate of
lime in solution with some of the alumina, and precipitates all the
phosphates as a white mass, consisting chiefly of tri-phosphate of lime.
To insure a thorough reaction and complete precipitation the steaming
must be uninterrupted for the sake of the agitation as well as the
heating which the steam currents produce. The whiting too must be
in sufficient quantity to neutralize all of the hydrochloric acid holding
in solution the phosphates, and that is about 0.65 pounds of dry whiting
for every pound of the phosphates in the raw material. A very short
time, or less than an hour, suffices to complete the precipitation of a large
vat full of liquor. When the liquor no longer effervesces upon the
addition of whiting, and the liquor above begins to clear quickly, these
are signs that all the phosphate is down, and the heating is to be dis-
continued and the whole left at rest for about half an hour or until
it settles. Then the clear supernatant liquor, which is wholly a solution
of chloride of calcium, must be drawn off to waste or for evaporation
into dry chloride of calcium if there should be a demand for the latter.
It is next necessary to add hydrochloric acid to a small sample of
the precipitate, so as to determine whether an excess of whiting has
been employed. If any effervescence ensues then this test answers in
the affirmative, and hydrochloric acid in dilute state must be added
cautiously to the whole of the precipitate in the vat during steaming
until there is no longer any carbonic acid given off. The heating is
then to be discontinued and the whole allowed to settle, and the clear
liquor drawn off into a similar vat to be precipitated anew with the
next batch of strong liquor. This is necessary to reclaim the small
quantity of phosphates which the acid may have also taken up while
dissolving out the excess of whiting. The precipitate is next thinned
with about its volume of fresh water heated for a few minutes by the
steam currents and allowed to settle. The clear supernatant liquor is
then drawn off as before in the precipitation vat adjoining. Again the
precipitate is to be washed with fresh water, but the wash water drawn
off this time is to be allowed to run to waste. The precipitate is now free

page_text: from all impurities, save a little alumina, oxide of iron, and some traces
of chloride of calcium. If the precipitate is to be sent into market as
such, then the traces of chloride of calcium must be removed, for if left
in they would impart a hygroscopic property which no subsequent
drying would destroy. Therefore to correct this tendency to dampness
and render the precipitate marketable it must be treated after the last
washing with an aqueous solution of about 50 to 100 pounds of
ammonium or potassium sulphate for about every ton of dry phosphate
in the precipitate and steamed as before for about fifteen minutes. All
of the chloride of calcium, by a double exchange of bases with the
alkaline salt is converted thus into solid sulphate of lime, while ammonium
or potassium chloride forms in solution. This latter after repose may bo
drawn off and evaporated to dryness and sold separately. But if the
precipitate is to be used as a fertilizer or manure the mixture should
be run directly upon the kiln and there dried to a pulverulent mass.
The alkaline chloride adds more than its cost to the value of the product,
and this latter treated as just prescribed will not only dry quickly but
will remain dry even in damp atmospheres. On the other hand the
presence of traces of chloride of calcium will not interfere with the
conversion of the precipitate into bi-phosphate of lime, and they need
not be removed when the precipitate is to be used for this latter product.
The precipitate is ready for the operation after the washings with water.
This operation consists in passing the pulp through a mixing mill of
conical or other shape in contact with sulphuric acid in such a manner
that they may come together simultaneously in chemical equivalent
proportions and pass out, after being well incorporated, into brickwork
enclosures, there to remain until it is dry and ready to be packed for
market. Assuming that the sulphuric acid is the commercial kind of
specific gravity 1.700, known as brown oil of vitriol, then about 0.81
pounds will be required for every per cent. or pound of dry phosphate of
lime in the precipitate. The pure state and pulpy condition of the fresh
precipitate enables the latter to pass wholly into superphosphate as
promptly as possible, and without any excess or waste of acid. In case
the bi-phosphate portion of the superphosphate is required to be freed
from its sulphate of lime associate, then it is only necessary to boil it in
a vat with water by steam currents, and after leaving the whole a
sufficient time for cooling and settling to draw off the supernatant liquid
phosphate of lime and evaporate it to dryness. To remove the last
traces of liquor which the residual solid sulphate of lime may retain it is

page_text: only necessary to submit the latter to the action of a turbine or centri-
fugal machine, such as is used in sugar refineries for separating the
molasses from the grain sugar. The more economical way however for
making puro bi-phosphate of lime is to let the fresh pulp and sulphuric
acid pass from the mixer into cylindrical vats of cast iron lined with
lead, and constructed so as to accomplish both the digestion and filtration
in one and the same vessel. The vat therefore is divided towards the
bottom by a perforated diaphragm in moveable segments, and when this
diaphragm is covered with a cloth and the mixture it forms a close
chamber beneath. To this close chamber is arranged an air pump
attachment, so that it may be exhausted of air from time to time as may
be necessary to hasten the filtration of the liquid from the solid portion.
The upper chamber is fitted with a stirrer and steam pipes for agitating
and heating the contents. The clear filtrate as it accumulates in the
lower chamber is drawn off through a tap and evaporated to dryness for
market as nearly pure bi-phosphate of lime. This arrangement allows
the use of chamber acids of feebler strength than specific gravity 1.700,
and thus saves largely on the cost of this material. In such cases the
quantity of weak acid employed must be equivalent to about 0.52 pounds
of dry sulphuric acid (S O₂) per pound of dry tri-phosphate of lime in
the precipitate.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Campbell Morfit in the Great Seal Patent Office
on the 13th October 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CAMPBELL
MORFIT, of Baltimore, Maryland, in the United States of America, but
at present of 35, Southampton Buildings, in the County of Middlesex,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirteenth day of April, in the year of
our Lord One thousand eight hundred and seventy-one, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Campbell Morfit, Her special licence
that I, the said Campbell Morfit, my executors, administrators, and
assigns, or such others as I, the said Campbell Morfit, my executors,
administrators, and assigns, should at any time agree with, and no

page_text: 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, tho
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS
IN THE MANUFACTURE OF PHOSPHATES OF LIME, AND IN APPARATUS EMPLOYED
therein," upon the condition (amongst others) that I, the said Campbell ·
Morfit, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands 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 Campbell Morfit, 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, that is to say :—
The Invention relates to the treatment of bones, bone ash, bone black,
and the mineral and crude phosphates of lime generally by certain
chemical and mechanical means for their conversion into highly refined
products.
The mode of carrying my Invention into effect is as follows:-The
raw phosphate material is reduced first to powder, and then put into
a vat. This vat is of flagstone or other material which will resist the
action of acid. As it is to serve the part of a digester it has a moveable
counterpoised lid hung over pulleys by chains, and furthermore is
enclosed by a wall so built and covered as to leave an intervening space
as a surrounding hot air chamber. Through this chamber and encircling
the exterior of the vat is a series of iron tubes with suitable taps for the
passage of steam as the means of heating. Hydrochloric acid is next
added to the powdered material in this vat to dissolve out all of the
carbonate of lime, phosphate of lime, and phosphate of magnesia, and
after the effervescence has subsided the cover is lowered and steam
passed through the tubes. The heating and digestion is then to be
continued judiciously as to time and temperature, so that as little as
possible of fluoride of calcium, aluminium, and iron compounds may be
taken up with the phosphates and carbonate. Assuming that the hydro-
chloric acid employed has a specific gravity of 1.17, then about 2.13
pounds will be required for every pound of carbonate of lime, and in

page_text: addition about 1.40 pounds for every pound of phosphates of lime and
magnesia which the raw material under treatment may contain. When
all the carbonate and phosphates have been taken up in solution by the
acid the digestion is finished, and the whole must be left to repose.
The clear upper liquor is then to be drawn off from the settlings beneath
into a separate vessel designated the precipitation vat. This vat may be
of wood covered with protecting paint or hard pitch, and must have
dipping into it several steam pipes as a means of heating its contents
when necessary. The settlings or insoluble residue are next to be
washed three several times with as many relays of fresh water, and after
each settling as before the wash water is to be drawn off into the
precipitation vat containing the previous stronger liquor. The settlings
being now exhausted and cleansed are to be thrown out as waste. The
liquor in the precipitation vat is an hydrochloric solution of all the
phosphates of the original or raw phosphate material. It contains also
the whole of the carbonate of lime and some of the alumina and oxide of
iron as chlorides. The next step is to separate the former from the
latter in a state wholly or nearly pure. This is done by heating the
liquor by means of steam currents to from 200° to 212° Fahrenheit, and
adding during the agitation and high temperature thus promoted that
kind of carbonate of lime known as whiting. The latter should be in
fine powder, and added through a sieve for its better distribution over
the entire surface of the liquor. It must be added by degrees and
always at such intervals between the doses as will allow the effervescence
from a previous portion to subside before the succeeding one is sifted in.
This treatment with whiting leaves the carbonate of lime in solution
with some of the alumina, and precipitates all the phosphates as a white
mass consisting chiefly of the tri-phosphate of lime. To insure a
thorough reaction and complete precipitation the steaming must be
uninterrupted for the sake of the agitation as well as the heating which
the steam currents produce. The whiting too must be in sufficient
quantity to neutralize all the hydrochloric acid holding in solution
the phosphates, and that is about 0-65 pounds of dry whiting for every
pound of the phosphates in the raw material. A very short time suffices
to complete the precipitation of a large vat full of liquor. When the
liquor no longer effervesces upon the addition of whiting, and the liquor
above begins to clear quickly, these are signs that all the phosphate
is down and the heating is to be discontinued and the whole left at rest
for about half an hour or until it settles. Then the clear supernatant

page_text: liquor which is wholly a solution of chloride of calcium must be drawn
off to waste or for evaporation into dry chloride of calcium if there
should be a demand for the latter. It may happen occasionally that
the liquor will show an acid reaction to blue litmus paper even after
the prescribed dose of whiting has been added, and in such case a more
protracted boiling is necessary. The next step is to add hydrochloric
acid to a small sample of the precipitate so as to determine whether an
excess of whiting has been employed. If any effervescence ensues then
this test answers in the affirmative, and hydrochloric acid in dilute state
must be added cautiously to the whole of the precipitate in the vat
during steaming until there is no longer any carbonic acid given off.
The heating is then to be discontinued and the whole allowed to settle,
and the clear liquor drawn off into a similar vat to be precipitated anew
with the next batch of strong liquor. This is necessary to reclaim the
small quantity of phosphate which the acid may have also taken up
while dissolving out the excess of whiting. The precipitate is next
thinned with about its volume of fresh water heated for a few minutes
by the steam currents and allowed to settle. The clear supernatant
liquor is then drawn off as before into the precipitation vat adjoining.
Again the precipitate is to be washed with fresh water, but the wash
water drawn off this time is to be allowed to run to waste. The precipi-
tate is now free from all impurities save a little alumina, oxide of iron,
and some traces of chloride of calcium. If the precipitate is to be sent
into market as such then these traces of chloride of calcium must be
removed, for if left in they would impart a hygroscopic property which
no subsequent drying would destroy. Therefore to correct this tendency
to dampness and render the precipitate marketable it must be treated
after the last washing with an aqueous solution of about 50 to 100
pounds of ammonium or potassium sulphate, for about every ton of dry
phosphate in the precipitate and steamed as before for about fifteen
minutes. All of the chloride of calcium by a double exchange of bases
with the alkaline salt is converted thus into solid sulphate of lime while
ammonium or potassium chloride forms in solution. This latter after
repose may be drawn off and evaporated to dryness and sold separately.
But if the precipitate is to be used as a fertilizer or manure the mixture
should be run directly upon a kiln bed and there dried to a pulverulent
mass. The alkaline chloride adds more than its cost to the value of
the product, and this latter treated as just prescribed will not only dry
quickly but will remain dry even in damp atmospheres. On the other

page_text: hand the presence of traces of chloride of calcium will not interfere
with the conversion of the precipitate into bi-phosphate of lime, and
they need not be removed when the precipitate is to be used for this
latter product.
The precipitate is ready for the operation after the washings with
water. This operation consists in passing the pulp through a mixing
mill of conical or other shape in contact with sulphuric acid in such a
manner that the two may come together simultaneously in chemical
cquivalent proportions and pass out after being well incorporated into
brickwork enclosures, there to remain until the mass is dry and ready to
be packed for market. Assuming that the sulphuric acid is the com-
mercial kind of specific gravity 1.700, known as brown oil of vitriol,
then about 0.81 pounds will be required for every per cent. or pound of
dry phosphate of lime in the precipitate. The pure state and pulpy
condition of the fresh precipitate enables the latter to pass wholly into
superphosphate" as promptly as possible and without any excess or
waste of acid. In case the bi-phosphate portion of this "superphosphate "
is required to be freed from its sulphate of lime associate, then it is
only necessary to boil it in a vat with water by steam currents, and
after leaving the whole a sufficient time for cooling and settling to draw
off the supernatant liquid, bi-phosphate of lime, and evaporate it to
dryness. To remove the last traces of liquor which the residual solid
sulphate of lime may retain it is only necessary to submit the latter to
the action of a turbine or centrifugal machine such as is used in sugar
refineries for separating the molasses from the grain sugar.
66
The more economical way however for making pure bi-phosphate of
lime is to let the fresh pulp and sulphuric acid pass from the mixer into
cylindrical vats of cast iron lined with lead and constructed so as to
accomplish both the digestion and filtration in one and the same vessel.
The vat therefore is divided towards the bottom by a perforated
diaphragm in moveable segments, and when this diaphragm is covered
with a cloth and the mixture it forms a close chamber beneath. To
this close chamber is arranged an air pump attachment so that it may
be exhausted of air from time to time as may be necessary to hasten
the filtration of the liquid from the solid portion. The upper chamber
is fitted with a stirrer and steam pipes for agitating and heating the
contents. The clear filtrate as it accumulates in the lower chamber is
drawn off through a tap and evaporated to dryness for market as nearly

page_text: pure bi-phosphate of lime. This arrangement allows the use of chamber
acids of even feebler strength than specific gravity 1.700, and thus
saves largely on the cost of this material. In such cases the quantity
of weak acid employed must be equivalent to about 0.52 pounds of dry
sulphuric acid (SO,) per pound of dry tri-phosphate of lime in the
precipitate.
I have not thought it necessary to give a Drawing of the arrangement
of the apparatus above described, as aided by the above description the
construction and mode of employing the same will be readily under-
stood.
Having thus described the nature of my said Invention and the mode
in which I carry the same into effect, I would have it understood that
what I claim is, the elimination of worthless matters from crude phos-
phates of lime and the separation of the valuable phosphate constituents
either as nearly pure dry precipitated phosphate of lime, commercial
"superphosphate," or pure bi-phosphate of lime in the manner and by
the mechanical and chemical means as herein-before substantially set
forth and described.
In witness whereof, I, the said Campbell Morfit, have hereunto
set my hand and scal, this Second day of October, in the year of
our Lord One thousand eight hundred and seventy-one.