462 
advantage, as the metal, during the process, becomes softer 
and finer in quality from the removal of other foreign 
matters. 
As an example of the purification of lead by this method, 
the following is a description of the results of some experi- 
ments made with a battery of four pots. The pots contained 
about six tons of lead. The metal employed being at the 
commencement, of very fair quality, as the accompanying 
analysis will shew : — 
In 100 Parts. 
No. 1. No. 2. 
Copper 000.0066 000.0154 
Iron 000.0065 000.0068 
Silver 000.0046 000.0052 
Sulphur Trace Trace 
The iron pots are set in brickwork, and rest upon a broad 
rim, the fire playing freely round the hemisphere. Dampers 
are provided to regulate the temperature, upon which 
the success of the process much depends. The lead is 
melted as rapidly as convenient, the temperature being far 
below red heat. Constant stirring facilitates the separation 
of impurities which rise to the surface, and are removed by 
skimming with the portion of oxidised lead. The impurities 
thus removed, will be the easily oxidisable metals when present, 
as iron, antimony, arsenic, together with sulphide of lead. 
After skimming, the fires are raked out and the lead allowed 
to cool. It is kept constantly stirred, and any portions which 
solidify round the edge of the pan are sliced off with the iron 
tool used in stirring, and thrust into the fluid metal. In about 
an hour-and-a-half or two hours time, small crystals of lead 
are formed, presenting a granular appearance in the melted 
mass. These are removed to the adjoining pot by means of 
a perforated ladle. The temperature then is carefully pre- 
served at the same point until a sufficient fraction has been 
taken out ; the bottoms, or enriched portion, is ladled into 
another pan. 
