MANUFACTURE OF MAGNESIA
Year: 1880

page_text: LETTERS PATENT to Thomas Twynam, of 22, Addison Gardens, North
Kensington, Chemist, for an Invention of
MANUFACTURE OF MAGNESIA."
"IMPROVEMENTS IN THE
PROVISIONAL SPECIFICATION left by the said Thomas Twynam at the Office
of the Commissioners of Patents on the 9th March 1880.
THOMAS TWYNAM, of 22, Addison Gardens, North Kensington, Chemist.
"IMPROVEMENTS IN THE MANUFACTURE OF MAGNESIA."
This Invention relates to an improved process for the preparation of magnesia,
free or nearly free from lime, from cheap or waste materials. I take a dolomite as
free as possible from silica and other foreign bodies, and as rich as possible in
magnesia, and burn it to lime. It is then ground finely and thrown into tanks.
A solution of chloride of calcium or chloride of magnesium and calcium, both of
which are waste products, is then run onto the lime and the whole well agitated
for some time, and after being allowed to stand is finally boiled up with steam pipes
or other convenient manner. The lime added to the solution should always be
sufficient to entirely precipitate any magnesia in the solution. If after boiling a
sample of the magnesia dissolved in hydrochloric acid being tested for lime shows
the presence of any considerable amount of lime, more chloride solution should be
added.
The magnesia is filtered off from the boiling liquor and is, when dried, ready for
use. The solution on cooling deposits crystals of oxychloride of calcium. When
magnesium chloride solution can be obtained cheaply it may with advantage be
substituted for calcium chloride.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Thomas Twynam in the Great Seal Patent Office on the 8th
September 1880.
THOMAS TWYNAM, of 22, Addison Gardens, North Kensington, Chemist.
"IMPROVEMENTS IN THE MANUFACTURE OF MAGNESIA."
This Invention relates to an improved and economical process for the preparation
of magnesia free or nearly free from lime.
I take a dolomite as free as possible from silica and other foreign bodies, and as
rich as possible in magnesia, and burn it to lime, taking care not to overburn it.
It is then ground or slaked with water and thrown into tanks or other convenient
vessels.
A solution of chloride of calcium (chloride of magnesium and calcium may be
used if available, both being waste products in various manufactures) is then run
onto the lime and the whole well agitated for some time, and after being allowed
to stand for from six to twenty-four hours is finally boiled up by the use of steam
pipes or other convenient manner. I sometimes find it convenient to boil under
pressure. The lime in the burnt dolomite should always be sufficient to entirely
precipitate any magnesia there may be in the solution used. If after boiling a
sample of the undissolved magnesia, on being tested, shows the presence of any
considerable amount of lime, more chloride solution should be added and the boiling
resumed.
The magnesia is filtered off from the liquor and is, when dried, ready for use; it
may be easily freed from any chloride of calcium by washing. The solution on
cooling deposits crystals of the oxychloride of calcium; these are decomposed by
cold water, forming a solution of chloride of calcium and leaving pure hydrate of
lime insoluble; the chloride of calcium is used again. The industrial uses of
magnesia are well known. I do not claim the production of magnesia by
precipitating it from its solutions by means of lime, but I claim,―
The preparation of magnesia from dolomitic lime by dissolving out the lime from
burnt magnesian lime by means of a solution of chloride of calcium, substantially
as herein described.
In witness whereof, I, the said Thomas Twynam, have hereunto set my
hand and seal, this Seventh day of September, in the year of our Lord
1990