ALUMINIUM. 



59 



Carbonate of lime. Limestone, or Chalk, CaO+CO^, is also found 

 native. — The purest varieties constitute marble. 



Prop, — Insoluble in water, but soluble if carbonic acid be present ; 

 exists in many natural waters, as a supercarbonate, and is deposited 

 from them as stalactites. 



The phosphate of lime exists in bones. 



Chlorine, iodine, bromine, fluorine, and sulphur form compounds 

 with calcium. 



Chloride of calcium is prepared by the action of hydrochloric 

 acid on carbonate of lime. It is distinguished for its great affinity 

 for moisture, and hence is of great use to the chemist in removing 

 water from substances ; also for forming frigorific mixtures. The 

 fluoride is found native diSfluor spar. 



Hypochlorite of lime, commonly called chloride of lime, is the 

 well-known bleaching powder ; — prepared by the action of chlorine 

 on thin strata of hydrate of lime. 



Test for lime, — Oxalic acid forms an insoluble oxalate, 



MAGNESIUM. 



Obtained by heating the chloride with potassium. It is a white, 

 malleable metal ; heated in the air, is converted into magnesia. 



Magnesia is the only oxide, MgO. — Prepared by driving off the 

 carbonic acid from the carbonate by heat. It is a soft, white, in- 

 soluble powder. 



Carbonate of magnesia occurs native ; may be easily prepared 

 by double decomposition ; — is very nearly insoluble. 



Sulphate of magnesia, Epsom salts, MgO-f SOg-fTHO, exists in 

 sea-water, and certain mineral springs ; it is very soluble ; forms 

 crystals of a right rhombic prism. 



Test for magnesia. — Forms the well-known Epsom salt with 

 sulphuric acid. 



SECTION III. 

 CLASS III. 



METALS OF THE EARTHS. 



This class includes Aluminium, Yttrium, Glucinium, Zirconium, 

 and Thorium. . 



ALUMINIUM. 



Prepared in the same manner as magnesium ; has a gray colour ; 

 of difficult fusibility ; forms alumina when burnt in the air. 



Alumina is a sesquioxide, AI3O3 ; exists abundantly throughout 

 nature, constituting the different sorts of clay ; prepared by adding 



