IMPROVEMENTS IN MAKING WHITE LEAD AND IN THE MEANS AND APPLIANCES FOR PERFORMING THE SAME
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by Isham Baggs at the Office
of the Commissioners of Patents, with his Petition, on the 25th
September 1868.
I, ISHAM BAGGS, of High Holborn, in the County of Middlesex, do
hereby declare the nature of the said Invention for "IMPROVEMENTS
IN MAKING WHITE LEAD AND IN THE MEANS AND APPLIANCES FOR PERFORMING
THE SAME," to be as follows :-
Where cast blue lead is employed for making white lead I cast the
metallic lead upon very hot plates or surfaces so as to obtain a thinner
cast having good surface and less weight than at present. I make the
white lead in pots or in any convenient receptacle, but I prefer the
use of chambers. In effecting corrosion I use nitric, nitrous, and acetio
acids, together or separately, with or in addition to carbonic acid,
atmospheric air, or oxygen, and I sometimes use to quicken the process
nitric, oxide, and peroxide of nitrogen. Heat is preferably employed,
and acid vapours and steam are blown into the chambers or brought

page_text: into contact with the blue lead or compound of lead to be operated upon
and from which the white lead is to be made.. In order to save the
waste of these vapours they are condensed by a worm or in any suitable
condenser, and so saved and used again and again, while the permanent
gases which escape action are allowed to pass onward. The worm or
condenser is preferably surrounded by cold water, and the condensed
liquor may be returned to the original supply continuously by a pipe.
I also employ a pump or pumps to throw into the chambers or receptacles
the requisite quantity of the several gases in the proportion of their
chemical equivalents or as may be otherwise determined in practice.
Any engine or machine acting by displacement may be similarly used
for the same purpose; and I register the quantities of air, gas, and
vapour thus operating by meters and counters as well understood. I
also employ in certain cases a draught or a propulsive power as from
a screw or jet of steam. The gases and vapours are made to enter and
circulate through the chamber or chambers in any convenient manner.
I also where advantageous supply a close chamber packed with blue
lead, with oxygen and carbonic acid, and the vapour of nitric, nitrous,
and acetic acids, together or separately, until the requisite combination
is effected and the white lead is produced; and where one of the oxides
of lead or any other source of oxygen is used in the chambers or
receptacles the oxygen may be dispensed with in the above mixture.
The chambers or receptacles are preferably heated and are used either
with or without pressure. I obtain the carbonic acid in some cases
from the gas now produced at breweries, distilleries, and wine factories
which is at present commonly wasted. In other cases I obtain carbonic
acid by heating the bicarbonates, and where convenient I procure and
employ this gas as produced in ordinary cases of combustion, obtaining
it for such purpose from the waste gases of furnaces, shafts, flues, and
other like sources, or from buildings where combustion or respiration is
carried on in sufficient quantity; and where necessary I purify the
carbonic acid from certain sources by passing it over or in contact with
oxide of iron. I find it advantageous in certain cases to alternately
heat and cool the chambers or receptacles in any convenient way so
as to cause the alternate dessication and precipitation of the acid fumes
upon the metal or compound to be corroded. Where it can be economi-
cally or beneficially effected I also employ coal or other inflammable
gas, petroleum, and hydrocarbons generally, to heat the chambers

page_text: or receptacles; and where desirable to furnish at the same time by
their combustion, either wholly or partially, the necessary supply of
carbonic acid and water required in making white lead.