A NEW OR IMPROVED PROCESS OF DISSOLVING THE LIME OUT OF PHOSPHATES OR OTHER CALCAREOUS MINERALS TO FORM A CAUSTIC SOLUTION CAPABLE OF REPLACING SODA IN CERTAIN OPERATIONS WITH CONSEQUENT ENRICHMENT OF THE RESIDUAL SUBSTANCE
Year: 1884

page_text: COMPLETE SPECIFICATION.
I MICHEL CAHEN, Engineer, of Brussels in the Kingdom of Belgium do hereby
declare the nature of my said Invention for A NEW OR IMPROVED PROCESS OF
DISSOLVING THE LIME OUT OF PHOSPHATES OR OTHER CALCAREOUS MINERALS
TO FORM A CAUSTIC SOLUTION CAPABLE OF REPLACING SODA IN CERTAIN
OPERATIONS WITH CONSEQUENT ENRICHMENT OF THE RESIDUAL SUBSTANCE and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
A boiling solution of chloride of calcium has the property of dissolving lime
and the saturated solution deposits crystals on cooling having the composition
Ca Cl + 3 Ca O+ 15 HO, or containing in 3430 parts, chloride of calcium
692 parts, caustic lime 1050 parts, water 1688 parts. In this state the lime
retains its caustic properties just as soda does when combined with fatty acids.
In nature we find various descriptions of lime stones, one in particular, which is
a mixture of carbonate and phosphate of lime in various proportions: the
percentage of phosphate of lime is often so small as not to add to the commercial
value of the limestone: now taking a limestone containing 20 per cent. of tribasic
phosphate of lime and about 80 per cent. of carbonate (or we might make use of
one containing 15 per cent. tribasic phosphate and about 85 per cent. carbouate of
lime), it would contain

page_text: This leaves 62 per cent. excess of caustic lime on account of which the phosphatic
mineral is still of too low a grade to be available for the production of super
phosphates; attempts have been made to remove the excess lime by methods based
on the difference in density of the substances, but without much success.
Now by my process, based upon the principle explained above, very superior
results are obtainable, and the working of the process has the further advantage
of producing a valuable product not hitherto obtained on a manufacturing scale.
In fact, by the method above indicated, I can remove practically the whole of the
448 kilos. of lime, leaving the phosphate of lime intact.
For this purpose, after having slaked the quick lime present in the calcined
mass of 648 kilos., I boil the same with a sufficiency of calcium chloride and
water.
17.
As stated 1050 parts of Ca O require 092 parts of dry Ca Cl, 300 kilos. will
therefore be theoretically requisite to dissolve the 448 kilos. in question, but a
slight excess facilitates the operation. Water is necessary in the proportion of at
least twice the weight of the slaked lime employed, or even more according to the
nature of the material under treatment; the solution should be easily separable
from the solid residuo whilst hot, by means of a filter press or other suitable
arrangement.
The tribasic phosphate of time-obtained by this process is nearly pure, and has
a relatively much greater value; being moreover-in-very-small grains it is easily-
rendered soluble or assimilable if required by the process described in Specification
No. 11,337 bearing even date with this application.
The filtrate constitutes a valuable detergent liquid. The detergent properties of
Fline water are well known, but owing to the comparatively slight solubility of
caustic lime in water, it is usually requisite to employ-milk-of-lime containing a
large quantity of-lime-in suspension; this excess lime deposits on the articles to
be washed and may burn or damage them, whilst the rinsing of the fabrics is-
thereby rendered difficult. -On-the-other hand, my_compound of lime and calcium
chloride contains a high percentage of quick lime, about 30 per cent., and the very-
soluble calcium chloride takes with it like the fatty matter of soaps, the substances
set free by washing and thus assists the operation materially. For commercial
purposes, this caustic lime solution may be concentrated out of contact with the
air and run into barrels before it cools. The chloride of calcium which forms the
basis of my operation is a waste product, at present unutilized, of several large
industries, moreover, for the purpose of acting on the phosphate alone, the chloride
may be revivified as often as desired, and for the purpose of producing a cleansing
compound I may make use of any source of quick lime available.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed, I declare that what
I claim is:
1st. The above described process of obtaining caustic lime solution of great
strength by dissolving quick lime in solution of chloride of calcium.
2nd. The process of obtaining tribasic phosphate of lime from poor lime
phosphates, which consists in extracting the excess of lime therefrom by means of
calcium chloride substantially as described.
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