404 



SCIENTIFIC RECREATIONS. 



earthen crucible 



lation ; the ores are mixed with the flux in a large 

 or pot. 



We have already noticed the alloy of zinc with copper (brass), and the 

 use of zinc to galvanize iron by covering the latter with a coating of zinc 

 in a bath is somewhat analogous to electro-plating. The metal is largely 

 used as the positive element in galvanic batteries, and for the production of 

 hydrogen in the laboratory. Zinc forms one oxide (ZnO), used for zinc- 

 white. The sulphate of zinc is white vitriol, and the chloride of zinc is an 

 "antiseptic." Certain preparations of the metal are used in medicine as 

 "ointments" or " washes," and are of use in inflammation of the eyelids. 



CHROMIUM. This " metallic element " is almost unknown in the 



metallic state. But although little 

 known, the beautiful colours of its 

 compounds make it a very interesting 

 study. The very name leads one to 

 expect something different to the other 

 metals chroma, colour. The metal is 

 procured from what is known as 

 chrome-ironstone, a combination of 

 protoxide of iron and sesqui-oxide of 

 chromium (FeOCr 2 O 3 ). By ignition with 

 potassium we get chromic acid and 

 chromate of potassium, a yellow salt 

 which is used to make the other com- 

 pounds of chromium. The metal is by 

 no means easy to fuse. 



Sesqui-Oxide of Chromium is a 

 fine green powder employed in paint- 

 ing porcelain. 



Chromate of Lead is termed- 

 " chrome yellow," and in its varieties is- 

 employed as a paint. 

 Chromate of Mercury is a beautiful vermilion. There are numerous- 

 other combinations which need not be mentioned here. 



Fig. 416. Type-casting. 



ANTIMONY was discovered by Basil Valentine. The Latin term is 

 Stibium, hence its symbol, Sb. It is very crystalline, and of a peculiar 

 bluish-white tint. It will take fire at a certain high temperature, and can 

 be used for the manufacture of " Bengal Lights," with nitre and sulphur in 

 the proportions of antimony " one," the others two and three respectively. 



The compounds of antimony are used in medicine, and are dangerous 

 when taken without advice. They act as emetics if taken in large quanti- 

 ties. Our " tartar emetic " is well known. 



Antimony, in alloy with lead and a little tin, form the type metal to 



