New Methods for the Manufacture of White-Lead.

The Manufacturer and Builder 7, 1870

The following new method for making white-lead has been patented in England, according to the London Mining Journal, by Messrs. Dale and Milner. The inventors propose to mix litharge, hydrated oxides of lead, or insoluble basic salts of lead, with an equivalent of bicarbonate of soda, together with sufficient water to form a stiff paste. This mixture is ground in a suitable mill, small quantities of water being from time to time added as may be found requisite, until the change of the lead bodies into carbonates in complete. The paste is now well washed with water, and the supernatant liquid, which contains the carbonate of soda, is separated from the white-lead by filtration, and boiled down to dryness and disposed of as soda-ash; or it may be crystallized, or may be again converted into bicarbonate of soda by treatment with carbonic acid, and used to convert further quantities of lead oxides or insoluble basic salts of lead into carbonates.

The same paper contains as an answer to a correspondent by Mr. W. R. Lake the suggestion to manufacture white-lead in the dry way in the following manner: Ordinary galena, is to be treated in an ore-crusher. It is then roasted in an ordinary desulphurizing kiln or oven, and then mixed with carbon, preferably in the state of fine washed pea or dust anthracite coal, in the proportion of half and half. He then jeats the mixture in a compound reducing and oxidizing furnaces, and dense white fumes or vapors pass off. These are conveyed into a separate chamber or receptacle, where the vapors are strained by passing through bags or screens of muslin or other fabric, or are allowed to deposit by being passed slowly through an extended chamber, in the way in which lamplback, oxide of zinc, etc., have been heretofore collected.

We doubt very much the success of the last method, because we can not see how by treating galena in this manner the formation of oxide of lead can be prevented, which would color the product yellowish, and consequently deteriorate it.