CALCIUM. 491 



cent of water of crystallization between 122 and 140, without 

 any other change. 



Nitrate of strontian generally crystallizes in octohedrons, 

 which are anhydrous, but it may be obtained at a low tempe- 

 rature in crystals of another form, which contain 5 HO. The 

 anhydrous salt dissolves in 5 parts of cold water, and in \ part 

 of boiling water. A deflagrating mixture, which produces an in- 

 tensely red illumination, is formed of 40 parts of nitrate of 

 strontian, 13 parts of flowers of sulphur, 5 parts of chlorate of 

 potash, and 4 parts of sulphuret of antimony. 



The salts of barytes, strontian and lead are strictly isomor- 

 phous, and greatly resemble each other in solubility and other 

 properties. 



SECTION VI. 



CALCIUM. 

 Eg. 256, or 20.52 ; Ca. 



Davy obtained evidence of the existence of this metal, and of 

 its analogy to the preceding metals. It is the basis of lime. 

 The name applied to it is derived from calx. 



Lime; Ca O;356, or 28. 52. Uncombined lime, or quicklime, 

 as it is termed in the arts, is obtained by heating masses of lime- 

 stone (carbonate of lime) to redness in a lime-kiln, or open fire. The 

 escape of the carbonic acid is favoured by the presence of the 

 aqueous vapour and gases of the fire, into which that gas can dif- 

 fuse (page 18J). In a covered crucible, carbonate of lime may be 

 fused by heat without decomposition. The lime remains in porous 

 masses, which may easily be separated from the ashes of the fuel, 

 and are sufficiently hard to be transported from place to place 

 without falling to pieces. Although these masses appear light, the 

 density of lime is not less than 2.3, or even 3.08, according to 

 Roget and Dumas. Water thrown upon them, is first imbibed, 

 and afterwards combines with the lime, which falls to powder 

 in the state of hydrate, and is then said to be slaked. In this 

 combination, the temperature rises sufficiently high to char 

 and kindle wood ; but the hydrate is decomposed, and lime is 

 made anhydrous by a red heat. From its affinity for water, 

 quicklime is applied to deprive certain liquids, such as alcohol, 



