IMPROVEMENTS IN REFINING SILVER LEAD, BY EFFECTING A SAVING IN ONE OF THE MATERIALS USED
Year: 1847

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ARTHUR
HARRY JOHNSON, of Gresham Street, in the City of London, Assayer, send-
greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Twenty-third day of
September, One thousand eight hundred and forty-seven, in the eleventh year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Arthur Harry Johnson, my exors, admors, and assigns, Her especial
licence, full power, sole privilege and authority, that I, the said Arthur Harry
Johnson, my exors, adiñors, and assigns, or such others as I, the said Arthur
Harry Johnson, my exors, admors or assigns, should at any time agree with,.
and no others, from time to time and at all times during the term of years
therein expressed, should and lawfully might make, use, exercise, and vend,
within England, Wales, and the Town of Berwick-upon-Tweed, in the
Islands of Jersey, Guernsey, Alderney, Sark and Man, and in all Her Majesty's
Colonies and Plantations abroad, my Invention of "IMPROVEMENTS IN REFINING
SILVER LEAD, BY EFFECTING A SAVING IN ONE OF THE MATERIALS USED;" in
which said Letters Patent is contained a proviso, that I, the said Arthur Harry
Johnson, shall cause cause a particular description of the nature of my said
Invention, and in what manner the same is to be performed, by an instrument
in writing under my hand and seal, to be inrolled in Her said Majesty's
High Court of Chancery within six calendar months next and immediately

page_text: after the date of the said in part recited Letters Patent, as in and by the same,
reference being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Arthur Harry Johnson, do hereby declare the nature of my said Invention,
and the manner in which the same is to be performed, are fully described
and ascertained in and by-the following statement-thereof, that is to say :-
My Invention consists in the following method of restoring after use and
rendering again available the phosphate of lime, or bone ash, whereof the
cupel or test is composed, which is used by refiners of silver lead, and is in their
process saturated with lead and a portion of silver.
To extract this lead and silver, the course as yet usually adopted is to return
the used cupel to the furnace, by which means the whole of the saturated
bone ash is destroyed, while a portion of the lead and silver combining with
the phosphoric acid of the bone passes off and is lost; by my improved method
little or no waste occurs of either the bone ash, silver, or lead.
My Invention consists in using a solvent of the oxide of lead, and I prefer
to conduct my process as follows:-I first reduce the used cupel to a tolerably
fine powder; I then add to it a sufficient quantity of pyroligneous or acetic
acid, carrying from the specific gravity of 1.030 to 1·048, according to the
per-centage of lead contained, so as to render it of a thin consistence, that it
may be thoroughly stirred, which I do by means of a "dolly tub," or some
.such convenient machine, or by allowing the acid to percolate through the
powdered test. After allowing the powdered cupel and acid to remain
together for two days (during which time I occasionally stir them well
together), the bulk of the lead becomes dissolved. I next turn the mixture
into cloth or flannel filters, or other convenient percolators, so as to allow the
said solution to drain off. This done, I remove the remaining soluble salt
of lead, by washing with water, and by the application of pressure previous
to drying the resulting bone ash.
By the process as above described the silver and some lead still remains in
the bone ash, though not sufficient lead to materially interfere with its absorbent
powers on again using, provided it has been properly freed from the lead solu-
tion. If, however, I wish to extract the lead more perfectly, I add a second
portion of the acid to the filtered or drained bone asb, and again thoroughly'stir
it in this second acid, the washing and pressing as before described following
this second operation.
To bring the lead contained in the solution into a marketable form, after due
saturation I either simply evaporate it in proper pans to make sugar of lead,

page_text: or by means of the several reagents commonly employed, I form respectively
the carbonate, the sulphate, the sulphuret, or other compounds of lead that
may be desired.
In place of the pyroligneous acid I sometimes use a solution of caustic
potash, or soda, containing about twenty per cent. of the pure alkali; but this
I have not found so useful.
In witness whereof, I, the said Arthur Harry Johnson, have hereunto set
my hand and seal, this Twenty-third day of March, in the year of
our Lord One thousand eight hundred and forty-eight.