Improvements in the Conversion of Hard Burnt into Soft Burnt Magnesia.
Year: 1890

page_text: Date of Application, 23rd July, 1890
Complete Specification Left, 23rd Apr., 1891-Accepted, 30th May, 1891
PROVISIONAL SPECIFICATION.
Improvements in the Conversion of Hard Burnt into Soft Burnt
Magnesia.
We, FARNHAM MAXWELL LYTE of 60, Finboro' Road, London, S.W.
Analytical Chemist, and JAMES GRAHAM TATTERS of The Manse, Runcorn,
Chester, Analytical Chemist, do hereby declare the nature of this invention to be
as follows:
The object of this invention is the conversion of hard burnt magnesia [MgO] say
that left from the generation of chlorine [Cl] into the soft burnt kind i.e. that which
has not been too strongly burnt, fitted for the decomposition of the double salt viz.
ammonic magnesic chloride, when heated with it for the production of magnesic
oxychloride and for other purposes.
We
Te profit by the manner in which hydrated chloride of magnesium [MgCl₂ 6 H₂O]
decomposes when heated into magnesia [MgO] mixed with comparatively little
magnesium chloride [MgCl,].
We dissolve the hard burnt magnesia [MgO] in aqueous hydrochloric acid
[HCI] and by evaporation to dryness the solution will be converted into a mixture
of magnesia [Mg] and magnesium chloride [MgCl,] with disengagement of weak
hydrochloric acid [HC1] say that there will be formed a mixture of 9 or
10 magnesia [MgO] and 1 magnesium chloride [MgC₁] the proportion, however,
of the two will vary according to circumstances.
The mixture which contains soft magnesia [MgO] may either be used by itself
after being heated to dull redness, any magnesium chloride present merely serving
to augment the amount of chlorine [Cl] in the oxychloride to be formed, or by
boiling with water the magnesium chloride [MgCl,] may be extracted and
magnesia [MgO] with more or less magnesium hydroxide [Mg(HO),] left.
Generally this mixture will be
3 MgO 2 H₂O MgO + 2 Mg(HO),-
=
By calcination, at a dull red heat, this mixture is entirely converted into
anhydrous soft burnt magnesia [MgO].
The concentrated solution of the chloride which has been solidified into an
oxychloride by the addition of some of the soft burnt magnesia [MgO] from a
previous operation, may also be completely decomposed by being heated to low
redness the decomposition being assisted if necessary by a current of steam. At
the end of the operation, all, or nearly all of the oxychloride will be found to be
converted into soft burnt magnesia [MgO] viz. that formed from the solution of
the hard burnt as well as the soft burnt that was added to solidify it, which will not
have altered.
Under all circumstances, the hydrochloric acid [HC1] driven off may be
recovered by condensation and except the first portion will be strong enough to be
used over again to dissolve more hard burnt magnesia [MgO]. Thus the same
operation may be continuously repeated with the same hydrochloric acid [HC1]
and any amount of magnesia [Mg0] be converted from the hard burnt into the soft
burnt kind.

page_text: COMPLETE SPECIFICATION.
Improvements in the Conversion of Hard Burnt into Soft Burnt
Magnesia.
We, FARNHAM MAXWELL LYTE of 60, Finboro' Road, London, S.W.,
Analytical Chemist, and JAMES GRAHAM TATTERS of The Manse, Runcorn,
Chester, Analytical Chemist, do hereby declare the nature of this invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
The object of this invention is the conversion of what is technically known as
"hard burnt" magnesia, say that left from the generation of chlorine, into the
"soft burnt" kind. By "hard burnt" magnesia is meant magnesia which having
been too strongly heated has become incapable of hydration by simple contact with
water and with difficulty attackable by the weaker acids; and by "soft burnt" is
meant that which not having been too strongly burnt has retained its affinity
unimpaired and is, amongst other purposes, fitted for the decomposition of the dry
double salt ammonic-magnesic. chloride when heated with it for the production of
magnesic oxychloride.
With this object we profit by the manner in which hydrated magnesic chloride
[MgCl, 6 H,O] decomposes, when heated, into magnesia mixed with comparatively
little magnesic chloride.
In carrying out our invention, we dissolve the hard burnt magnesia in aqueous
hydrochloric acid and by evaporation to dryness, the solution will be converted into
a mixture of magnesia and magnesic chloride with disengagement of weak hydro-
chloric acid, say that there will be formed a magnesic oxychloride of varying
composition consisting generally of a mixture of 9 or 10 parts of magnesia and 1 of
magnesic chloride; the proportion of the two varies, however, according to
circumstances.
The oxychloride or mixture thus formed is then heated to dull redness, the
operation being greatly assisted by first breaking up the material into fragments
and blowing in a current of steam, whereby soft burnt magnesia is formed, any
magnesic chloride left with the magnesia merely serving to augment the amount of
chlorine in the oxychloride to be formed by the decomposition of double ammonic-
magnesic chloride, which is one of the purposes for which soft burnt magnesia is
required.
If, however, the presence of the said magnesic chloride in the soft burnt
magnesia should be objectionable, it may be extracted by boiling the soft burnt
mass with water, magnesia with more or less magnesic hydroxide, being left.
Generally, the composition of this residue will be
or thereabouts.
3 MgO 2 H₂O = MgO + 2 Mg(HO),
By calcination at a dull red heat this mixture is entirely, or nearly entirely,
converted into anhydrous soft burnt magnesia.
or thereabouts.
3 MgO 2 H₂O = MgO + 2 Mg(HO),
By calcination at a dull red heat this mixture is entirely, or nearly entirely,
converted into anhydrous soft burnt magnesia.
An alternative method of procedure to dissolve the hard burnt magnesia in
hydrochloric acid as before, then concentrate the solution, and then add some soft
burnt magnesia, say that from a previous operation, to the concentrated solution for
the purpose of solidifying it into an oxychloride, which, like that produced by the
former method, may also be completely decomposed by being broken into morsels
of convenient size and being heated to low redness, the decomposition being
assisted, if necessary, in this as well as in the former case, by a current of steam.
At the end of the operation all, or at any rate nearly all, of the oxychloride will
have been converted into soft burnt magnesia, riz. that formed from the solution of
the hard burnt as well as the soft burnt that was added to solidify it which latter
will not have been altered by too strong heating and so the whole will be "soft
burnt."
4

page_text: Under all circumstances the hydrochloric acid driven off may be recovered; by
condensation and, except the first portion, will be strong enough to be used over
again to dissolve more hard burnt magnesia. Thus, the same operation may be
continuously repeated with the same hydrochloric acid with but little, if any, loss
and any amount of magnesia be converted from the hard burnt into the soft burnt
kind.
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 :-
:―
1st. The herein described method of converting "hard burnt" magnesia into
"soft burnt" magnesia or into magnesia with unimpaired affinities, which process
consists in dissolving the "hard burnt" magnesia in hydrochloric acid, evaporating
the solution to dryness or nearly so, and heating the residue to a temperature not
exceeding dull redness with or without the assistance of steam, substantially as
above described.
2nd. The herein described method of converting "hard burnt" magnesia into the
"soft burnt" modification which consists in dissolving the "bard burnt" magnesia
in hydrochloric acid, concentrating and solidifying the concentrated solution of
magnesic chloride into an oxychloride by the addition of "soft burnt" magnesia
and heating it to dull red with or without the assistance of steam, substantially as
above described.
3rd. The herein described continuous series of operations in the process of
converting "hard burnt" into "soft burnt" magnesia, which consists in dissolving
it in hydrochloric acid, converting it into an oxychloride, heating to redness,
condensing the aqueous HCl given off and employing the same hydrochloric acid
over again to dissolve more "hard burnt" magnesia and so on repeatedly as
specified.
1001