68 GEATES. 



geate of magnesia. It is decomposable by alkalies, 

 and then both acid and base are dissolved. The 

 geates of lime and magnesia when exposed to air, 

 absorb carbonic acid; a salt is formed, containing 

 an excess of geine — that is, the carbonic acid unites 

 with a part of the lime. These super-geates, as they 

 are termed, are always much more soluble, than the 

 neutral geates. 



121. Geate of alumina, is soluble in water, and 

 in alkali, without decomposition. It requires 4200, 

 parts of water to dissolve it, but is abundantly solu- 

 ble in alkali. 



122. Geate of iron requires 2300 parts of water 

 to dissolve it. Like geate of alumina, it dissolves 

 easily in alkaline carbonates. 



123. Geate of manganese requires 1450 parts of 

 water to dissolve it, and though soluble in ammonia, 

 is insoluble in potash or soda. 



124. The properties of the geates are of the 

 highest practical importance. The three earths, lime, 

 magnesia, and alumina, are universal constituents of 

 soil, and the two first are constantly present in plants. 

 In their relation to geine, these all combine with 

 that, they all form soluble compounds in the moist 

 state, but after having been thoroughly dried, these 

 geates are insoluble, even sun baking diminishes 



