IMPROVEMENTS IN THE PRODUCTION of Phosphates TO BE USED AS FERTILIZING AGENTS
Year: 1871

page_text: PROVISIONAL SPECIFICATION left by Robert Irvine at the Office
of the Commissioners of Patents, with his Petition, on the 5th
January 1871.
I, ROBERT IRVINE, of Baltic Street, Leith, North Britain, Chemist,
do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN THE PRODUCTION of Phosphates TO BE USED AS FERTILIZING AGENTS,” to be as
follows:-
.
This Invention relates to the production of phosphate of lime or
· magnesia for use as fertilizing agents, and consists, firstly, in treating
bones, bone ash, coprolites, apatite, Spanish phosphates, indeed all
materials at present vended as containing phosphates, such as guano
and the like, with hydrochloric (or muriatic) acid, so as to render soluble
the insoluble phosphate of lime contained therein (and commonly known
as insoluble bone phosphate). This I effect in a manner well known,
cither with or without the aid of heat.
Having obtained the tribasic phosphate of lime in a soluble form, and
consequently free from all the insoluble matter present in the raw

page_text: material so treated, I take the solution so formed and evaporate it to
complete dryness in pans or specially constructed furnaces, and there-
after incinerate or roast the residue so obtained until the free phosphoric
acid or acid phosphate of lime present has reacted upon the chloride
of calcium formed by the action of the hydrochloric (or muriatic)
acid upon the lime in the phosphate under treatment. By this means
I secure the reformation of tribasic or insoluble phosphate of lime
associated with an amount of chlorides of calcium or magnesium equi-
valent to the carbonates of those metals present in the raw material
acted upon by the hydrochlorić (or muriatic) acid in the first and well
known portion of this process. I remove these chlorides from the
insoluble phosphates by means of either hot or cold water, or I add
an equivalent quantity of phosphoric acid or acid phosphate of lime
sufficient to decompose the chlorides present. This I may do to the
solution of phosphates in hydrochloric (or muriatic) acid as it is first
formed from the raw material or add the same to the phosphates already
rendered insoluble by incineration and still retaining chlorides of calcium
or magnesium.
I
Having obtained nearly pure tribasic phosphates of lime or magnesia
may either use them by themselves or decompose them with sulphuric
acid and so form a compound containing soluble phosphate of lime or
magnesia suitable for use as fertilizing agents and containing a high
per-centage of soluble phosphates. The hydrochloric acid vapour given
off during the above-mentioned processes may be conducted into suitable
condensers and recovered for use in again acting on the before-mentioned
raw materials.
The second part of my Invention consists in partially evaporating the
solution of phosphates of lime in hydrochloric acid until the solution
becomes of a pasty consistency due to the formation of a modification
of phosphate of lime soluble in water but less soluble in the acid solution
containing chloride of calcium associated with it. This pasty mass I
transfer from the evaporators, when cold, to a filter composed of cloth
or to other suitable form of filter, and allow as much liquid to drain off
as will remove with it the excess of chloride of calcium present. The
partially soluble phosphate may then be washed with a little cold water
to remove still more of the soluble chlorides. I procure by this means
phosphate of lime soluble in water, but contaminated with chloride of

page_text: calcium, and to remove the last traces of this I ignite the residue so
left at a bright red heat. The acid phosphate reacts upon the chloride
present, and the product left is either wholly composed of a lower
phosphate or partially of tribasic phosphate of lime with a proportion of
the lower phosphate referred to.