317] SCIENTIFIC MANUAL. 31 



is generally used for this purpose, because of its cheap- 

 ness. 



Galvanized Iron is merely iron covered with a thin coat- 

 ing of zinc, which prevents it from rusting. Telegraph 

 wire is so protected. 



Iron Pyrites, a very common mineral, is a combination 

 of sulphur and iron. It is brittle, and has a bright, yellow 

 appearance, so nearly like that of gold that it is often 

 called " fools' gold," from the fact that many persons have 

 been deceived by it. The test is simply roasting the pow- 

 dered material in a shovel, when the odor of burning sul- 

 phur will be recognized, and the mass will change color. 

 One of its principle uses is in the manufacture of sulphu- 

 ric acid. 



Sulphate of Iron, known as copperas, or green vitriol, is 

 made from iron pyrites. It is used in dyeing, making ink 

 and medicinally. 



Spring Waters are often impregnated with iron, which 

 has been dissolved by the water while passing over beds of 

 ore in the earth. On exposure to the air the dissolved 

 iron is oxidised, and forms a scum on the surface, or a yel- 

 low deposit on the sides and bottom of the spring. These 

 are called chalybeate springs, and have valuable tonic prop- 

 erties. 



Arsenic and Antimony occur in nature in several forms. 

 Their use is chiefly in medicine. 



"Scheele's Green" is a poisonous compound of arsenic 

 and copper, which is in extensive use. It forms most of 

 the bright, green colors of wall paper. Its use should be 

 avoided, since metallic arsenic and another extremely poi- 

 sonous form of arsenic is set free, and floats in the atmos- 

 phere of rooms covered with such paper. 



"Paris Green," another salt of arsenic with copper, has 

 been used to kill the cotton worm and potato bug. It, too, 

 is a dangerous substance. 



The usual form of antimony used in medicine is tartar 



