106 METALLOSALINES. [IV. 



nish than white-lead. Another important advantage cannot 

 he overlooked : its freedom from the noxious character of 

 carhonate of lead on those who employ it. It is less drying 

 than white-lead colors, hut in ordSc to effect this result in a 

 shorter time, dry sulphate of zinc (white vitriol) may he added 

 to it, or a more drying oil may be employed. It has been too 

 lately introduced to decide upon the relative merits of the 

 several compounds above named, and it is even doubtful which 

 can be produced at the cheapest rate ; but it may be safely 

 assumed, from its low equivalent (32.6, H=l), that a given 

 weight of zinc will produce a much larger amount of white 

 pigment than the same weight of lead, with an equiv, = 104. 

 On the other hand, the objections to it are, that it has far less 

 body (covering power) than white-lead, and that it requires a 

 large amount of oil as its vehicle of conveyance to a surface. 



Durahility of Zine-wMte. — Lassaigne drew attention, in 

 1821, to the use of oxide of zinc instead of white-lead as a 

 pigment. He has lately stated that an oil-painting, finished 

 with oxide of zinc, has remained of a pure white to this day. 

 The oil was previously treated with sulphate of zinc to render 

 it more di'ying. 



Oxides of Zinc and Antimony, ^c. — It has been an object 

 of several patents, of late, to distil ores of zinc and antimony 

 in such a manner that the volatilized and oxidized products, 

 white oxides of antimony or zinc, shall be separately collected 

 and used as pigments. To avoid the cost of first obtaining 

 the metallic zinc and then converting it into oxide, the ores 

 are heated in furnaces of various construction, but so arranged 

 that the products of combustion from the mixed ore and fuel 

 are conducted into condensing chambers, where both metal 

 and oxide are obtained. Notwithstanding the ingenious con- 

 trivances for effecting this result, none have been yet found 

 faultless. One of the late patents on this subject (Lond. 

 Journ. Sept. 1850) subjects copper and other unroasted ores 

 to the action of a blast-furnace, so that the non-volatile pro- 

 ducts are obtained in the furnace, while the volatile are con- 

 densed in chambers. In this manner oxides of zinc, antimony, 



