TIX. 



403 



which painters are subject. 'Red lead, or minium, is a compound of the 

 protoxide and the binoxide, and may be found native. The former oxide 

 is litharge ; white lead, or the carbonate of lead, is a paint, ^ 



and is easily obtained by passing a stream of carbonic acid 

 into a solution of acetate of lead. It is used as a basis of 

 many paints. 



Tix is another well-known metal. It is mentioned 

 by Moses. It possesses a silver-like lustre, and is not 

 liable to be oxidised. The only really important ore is called 

 Tinstone, from which the oyxgen is separated, and the metal 

 remains. Cornwall has extensive tin mines. Tin is malleable 

 and ductile, and can be beaten into foil or " silver leaf," or 

 drawn into wire. It prevents oxidation of iron if the latter 

 be covered with it, and for tinning copper vessels for culinary 

 purposes. The Romans found tin in Cornwall, and the 

 term "Stanneries" was applied to the courts of justice among 

 the tin miners in Edward the First's time. We have already 

 mentioned the alloys of tin. The oxides of tin, " Stannous " 

 and " Stannic," are useful to dyers. The latter is the tin- 

 stone (SnOJ. . Sulphide of tin is called " Mosaic gold," and 

 is much used for decorative purposes. 



ZINC is procured from calamine> or carbonate of zinc, 

 and blende^ or sulphide of zinc. It has for some years been 

 used for many purposes for which lead was once employed, 

 as it is cheap and light. Zinc is a hard metal of a greyish 



colour, not 

 " .| - . 



Fig. 415. Preparing lead for bullets. 



tempt to smelt its ores. Zinc is 



easily bent, 



and rather Fig. 414. -section of 



shut tower. 



brittle; but 



when made nearly red-hot, 

 it can be rolled out into 

 sheets or beaten into form 

 by the hammer. Zinc is 

 about six-and-three-quarter 

 times heavier than water. 

 Like many other metals, it 

 is volatile (when heated to 

 a certain extent it passes off 

 into vapour), and the pro- 

 bable reason that it was not 

 known or used of old is 

 that it was lost in the at- 

 now obtained by a sort of distil- 



