492 CALCIUM. 



of the water they contain. It is obtained in a suitable state of 

 division for that purpose, by submitting to calcination in a 

 crucible the hydrate of lime itself, or by calcining 2 parts of 

 hydrate mixed with 3 of pulverulent chalk. For pure lime, the 

 crystallized carbonate should be calcined, such as calcareous 

 spar, or Carrara marble. Lime, in common with other infu- 

 sible earths, phosphoresces strongly when heated to full red- 

 ness. 



The hydrate of lime contains 1 eq. of water, which it loses 

 at a low red heat. It is sparingly soluble in water, but more 

 soluble in cold than in hot water. According to Dalton, lime- 

 water formed at 60, 130 and 212, contains 1 grain of lime in 

 778, 972 and 1270 grains of water. Hence, water saturated 

 in the cold, deposits hydrate of lime, when boiled. By evapo- 

 rating the solution in vacuo, Gay-Lussac obtained hydrate of 

 lime in small transparent crystals of the hexahedral form. The 

 milk or cream of lime is merely the hydrate diffused through 

 water. Lime-water has a harsh acrid taste, is alkaline, and, to 

 a certain extent, caustic, It precipitates carbonic, silicic, boracic 

 and phosphoric acids from solutions of their alkaline salts. It 

 dissolves oxide of lead. Lime-water absorbs carbonic acid 

 rapidly from the air, and becomes covered by a pellicle of car- 

 bonate of lime. Hydrate of lime has the same property, ab- 

 sorbing about half an equivalent of carbonic acid with avidity, 

 but not acquiring quite so much as three -fourths of an equi- 

 valent by 2 or 3 weeks' exposure to an atmosphere of the gas. 

 Fuchs observes, that when hydrate of lime is exposed to air, 

 it absorbs only half an equivalent of carbonic acid, and a de- 

 finite compound of hydrate and carbonate is formed. In the 

 anhydrous condition, lime exhibits no affinity for carbonic 

 acid. 



Lime is characterized by affording a bulky precipitate of 

 sulphate of lime, when sulphuric acid is added to its soluble 

 salts. But as the sulphate of lime has a certain degree of so- 

 lubility, this precipitate does not appear in very dilute solutions 

 of these salts, nor in lime-water, a property by which lime may 

 be distinguished from barytes and strontian. Sulphate of lime 

 may also, when separated, be re-dissolved by the addition of 

 nitric acid. Lime is entirely precipitated from neutral solutions, 

 by oxalate of ammonia, the oxalate of lime being completely 

 insoluble. In the quantitative estimation of this earth, it is 



