A text-book on chemistryFor the use of schools and colleges . white marbles are those which come from Paros,Pentelicus, and Carrara. It occurs pure in the form ofIceland spar in rhomboiclal crystals possessed of doublerefraction. It is dimorphous, and assumes the form ofsix-sided prisms in the mineral called Arragonite. It isanhydrous, insoluble in water, but in water chargedwith carbonic acid it is soluble, and is deposited fromsuch a liquid on boiling, or by the diffusion of the car-bonic acid into the air. The cart>onic acid is expelledfrom this salt by a red heat and the action of the m
A text-book on chemistryFor the use of schools and colleges . white marbles are those which come from Paros,Pentelicus, and Carrara. It occurs pure in the form ofIceland spar in rhomboiclal crystals possessed of doublerefraction. It is dimorphous, and assumes the form ofsix-sided prisms in the mineral called Arragonite. It isanhydrous, insoluble in water, but in water chargedwith carbonic acid it is soluble, and is deposited fromsuch a liquid on boiling, or by the diffusion of the car-bonic acid into the air. The cart>onic acid is expelledfrom this salt by a red heat and the action of the morepowerful acids. Carbonate of lime may be obtained inunion with water by boiling hydrate of lime with sugar. The formation of stalactites and stalagmites in cavesdepends on the solubility of carbonate of lime in car-bonic acid water. As the water trickles from the roofthe carbonate is partly deposited in the inverted conesuspended from the roof, called the stalactite, and part-ly in the cone, the stalagmite, on the floor, as seen inFig. 283. Fig. 283. -ME. Sulphate, of Lime, or Gypsum, occurs native both in What are the forms of carbonate of lime ? When does it dissolvein water? What arc stalagmites and stalactites? 330 SALTS OF LIME. crystals and in extensive crystalline masses. It con=tains two atoms of water, and forms selenite. Alabas-ter is also a sulphate of lime. Anhydrite contains nowater. On calcining the hydrous sulphate of lime at alow red heat it becomes plaster of Paris, and has theproperty of setting into a hard mass when made into apaste with water. It is then used for making plastercasts and for hard-finishing wTalls. The sulphate oflime is soluble in 500 parts of water, and communicateshardness to it, so that it becomes unfit for washing andcooking purposes. Phosphate of Lime, or Bone-earth, is a tribasicphosphate. It is precipitated when the ash of bones isdissolved in hydrochloric acid, and the solution neutral-ized by ammonia. It exists native as phosphori
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