AN IMPROVED PROCESS FOR PREPARING HYDRATE OF MAGNESIA
Year: 1874

page_text: LETTERS PATENT to William Edward Newton, of the Office for Patents,
66, Chancery Lane, in the County of Middlesex, Civil Engineer,
for the Invention of "AN IMPROVED PROCESS FOR PREPARING HYDRATE
OF MAGNESIA." -A communication from abroad by Charles H.
Phillips, of the City and State of New York, United States of
America.
Sealed the 14th August 1874, and dated the 21st May 1874.
PROVISIONAL SPECIFICATION left by the said William Edward
Newton at the Office of the Commissioners of Patents, with his
Petition, on the 21st May 1874.
I, WILLIAM EDWARD NEWTON, of the Office for Patents, 66, Chancery
Lane, in the County of Middlesex, Civil Engineer, do hereby declare
the nature of the said Invention for "AN IMPROVED PROCESS FOR PREPARING
HYDRATE OF MAGNESIA," to be as follows:-
-

page_text: denominates "milk of magnesia." This is effected by causing a solution
of ammonia to act on and decompose any suitable soluble salt or com-
pound of magnesia, so as to precipitate all the magnesia in the form
of an hydrate.
The magnesia compounds which it is preferred to use for the purposes
of the Invention are the chloride or the sulphate. The magnesian salt
should be dissolved in water, and the solution of ammonia may then be
added gradually, during which time the mixture must be kept constantly
stirred in order to prevent coagulation. The ammonia is added until
complete reaction has taken place, and the magnesian salt has become
perfectly decomposed. The mixture is then to be allowed to stand for
twenty-four hours, more or less, to settle, when the supernatant liquor
may be drawn off. The residuum or precipitate consisting of a hydrate
of magnesia is then washed repeatedly until the product is rendered
pure.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Edward Newton in the Great Seal Patent
Office on the 20th November 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
EDWARD NEWTON, of the Office for Patents, 66, Chancery Lane, in the
County of Middlesex, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-first day of May, in the year
of our Lord One thousand eight hundred and seventy-four, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said William Edward Newton, Her special
licence that I, the said William Edward Newton, my executors, admini-
strators, and assigns, or such others as I, the said William Edward Newton,
my executors, administrators, and 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 "AN IMPROVED

page_text: PROCESS FOR PREPARING HYDRATE OF MAGNESIA," being a communication
to me abroad by Charles H. Phillips, of the City and State of New
York, United States of America, upon the condition (amongst others)
that I, the said William Edward Newton, my exccutors, or admini-
strators, 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 William Edward Newton, 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 (that is to say) :-
This Invention relates to improvements in the mode of making the
medical compound termed "milk of magnesia," for which I obtained
Letters Patent dated January Sixth, One thousand cight hundred and
seventy-four, No. 72, and which compound consists of a pure hydrate
of the oxide of magnesium suspended in water. As previously prepared
great difficulty was experienced in making it so as to get it absolutely
free from the remnants of the sulphates of the alkalies used in pre-
cipitating the magnesia from its form as a sulphate or chloride to its
desired form as a hydrate in a pure state. To facilitate this process
is the object of the present Invention, which consists in resolving the
magnesia from its state as a sulphate or other soluble salt of magnesia
to a hydrate by the aid of ammonia, preferably liquor ammonice, or a
solution of the carbonate of ammonia.
To make one hundred gallons of the "milk of magnesia" by the
improved process, I take one hundred and twenty-five pounds of the
pure sulphate of magnesia and dissolve the same in about two hundred
gallons of distilled water, filtering it through paper if considered necessary
or desirable. To this is then added sufficient liquor of ammonia to free
and precipitate the magnesia from the sulphuric acid with which it is
combined. For this purpose from thirty to eighty pounds of the liquor
of ammonia, according to the strength of the preparation, are requisite
to produce the desired result.

page_text: Or instead of using liquor ammoniæ as the means of forming the
hydrate of magnesia, the carbonate of sesqui-carbonate of ammonia may
be substituted therefor, in which case enough must be taken to entirely
precipitate the magnesia. From sixty to eighty pounds will be found
sufficient for the purpose for every one hundred and twenty-five pounds
of the sulphate of magnesia taken. And as the most of the ammonia
can be reclaimed, whether as a sulphate or carbonate, or as ammoniacal
gas, by subjecting the clear liquor when drawn off to any of the well-
known processes for its manufacture in a condensed form it may (at
little cost) be used in excess so as to insure a perfect precipitation of the
whole of the magnesia.
When the carbonate is used it is better to use a moderate degree of
heat at first to effect the precipitation of the magnesia, after which it
may be brought to the boiling point and continued for a few minutes,
which will effect a thorough chemical dissolution of the sulphate of
magnesia, resolving it into a hydrate and forming simultaneously there-
with a sulphate of ammonia, and setting free the carbonic acid with
which the ammonia was previously charged.
If desired the boiling process may be prolonged sufficiently long to
expel all the sulphate of ammonia, after which the magnesia may be
allowed to settle as before, the liquor drawn off, and the magnesia then
washed twice or three times with distilled water, either cold or with
heat, and with agitation, each time allowing it to settle, and then drawing
off the liquor, until it has been sufficiently washed to remove all trace
of the ammonia or other impurities with which it may have been charged
or mixed.
When the ammonia is driven off by boiling directly from the magnesia
after the reaction has taken place, the vat or boiler in which the mixture
is contained should be provided with a suitable cover and worm through
which the products of distillation may be conducted into the receiver
in which the ammonia is to be reclaimed. The boiling need not con-
tinue longer than is absolutely necessary to expel the ammonia. The
sulphate and excess of other kinds of ammonia thus driven off may be
condensed in any known way, and afterwards treated with soda or
other suitable material to set free the ammoniacal gas, and which being
again condensed in water will form the necessary liquor ammoniæ for

page_text: the next vat full of magnesia which is to be reduced to the state of a
hydrate. Thus, the same ammonia may be used over and over again,
but little additional fresh ammonia being required for each new vat full
of the magnesian solution. The pure hydrate of magnesia thus obtained
is then mixed with the necessary amount of pure distilled water to make
it of the consistency required, and which is termed "milk of magnesia,"
each one hundred and twenty-five pounds of the sulphate yielding about
one hundred gallons of "milk of magnesia" of the consistency required.
About twenty grains of the pure hydrate will be found in every fluid
ounce of the so-called "milk of magnesia;" but it may be charged with
more or less as required by simply increasing or diminishing the quantity
of water with which it is mixed.
If absolute purity of the hydrate is required the process of washing
the magnesia may be repeated as often as may be deemed necessary;
but for all practical purposes (when heat is applied) two or three
washings will be found abundantly sufficient to remove any reasonable
amount of excess of the ammonia used for the precipitation of the
hydrate of magnesia, or the removal of its resultant sulphate.
Instead of using the sulphate of magnesia as the source of procuring
the hydrate, any other pure soluble salt of magnesia may be used, such
as the chloride of magnesium, simply taking care to use a sufficiency
of the ammonia to effect the necessary chemical change, the resultant
mixture being treated in precisely the same manner as before. The
only difference in the process when the chloride is used is the formation
of a hydrate of magnesia, and a muriate instead of a sulphate of
ammonia. The sulphate of magnesia is however preferred, as there
is a more abundant source of the raw material than there is of the
other..
Having now described the Invention which has been communicated
to me by my foreign correspondent, and having explained the manner
of carrying the same into effect, I claim as the Invention secured to me
by Letters Patent as aforesaid, the process herein described of preparing
hydrate of magnesia, to wit, by subjecting a soluble salt of magnesia
to the action of ammonia or carbonate of ammonia, as herein set
forth.
I also claim, preparing a milk of magnesia from such hydrate so

page_text: obtained by mixing the hydrate of magnesia with a suitable quantity of
distilled water, as described.
In witness whereof, I, the said William Edward Newton, have
hereunto set my hand and seal, the Tenth day of November,
in the year of our Lord One thousand eight hundred and seventy-
four.