488 BARIUM. 



precipitated carbonate loses its carbonic when calcined at a 

 white heat, in contact with carbonaceous matter. It is obtained 

 in greater purity when precipitated by the carbonate of ammonia, 

 than by the carbonate of potash or soda, portions of which are 

 apt to go down in combination with carbonate of barytes. Al- 

 though reputed an insoluble salt, carbonate of barytes is soluble 

 in 2300 parts of boiling water, and in 4300 parts of cold 

 water. It is still more soluble in water containing carbonic 

 acid, and is highly poisonous. The precipitated carbonate of 

 barytes is employed in the analysis of siliceous minerals, con- 

 taining an alkali, which are not soluble in an acid. The mineral, 

 in the state of an impalpable powder, is intimately mixed with 

 4 or 5 times its weight of this carbonate, and exposed in a pla- 

 tinum crucible to a white heat, which occasions a semi-fusion 

 of the mixture and the decomposition of the silicates ; the 

 mineral afterwards dissolving entirely in an acid, with the ex- 

 ception of its silica. 



Sulphate of barytes ; Ba O, SO 3 ; 1458, or 119.56. -This salt 

 consists, in 100 parts, of 34.37 sulphuric acid and 65.63 barytes. 

 The density of heavy spar, or the native sulphate, varies from 4 to 

 4.47. It occurs in considerable quantities, in trap and other ig- 

 neous rocks, forming often veins of several feet in thickness, and 

 miles in extent. It is mined for the purpose of being substituted 

 for carbonate of lead, or being mixed with that substance, when 

 used as a pigment. When chloride of barium is added to sul- 

 phuric acid, or to a soluble sulphate, at the boiling temperature, 

 sulphate of barytes precipitates readily, in a dense crystal- 

 line powder, which may easily be washed and collected on a 

 filter. It is completely insoluble in water and dilute acids ; 

 but is soluble in concentrated and boiling sulphuric acid, from 

 which it crystallizes on cooling. Precipitated sulphate of ba- 

 rytes is partially decomposed in a concentrated and boiling 

 solution of carbonate of potash or soda, and carbonate of barytes 

 formed. 



Nitrate of barytes ; Ba O, NO 5 5 1633.9, or 130.93. This 

 salt crystallizes in fine transparent octohedrons, which are an- 

 hydrous. It is obtained by dissolving carbonate of barytes in 

 nitric acid, diluted with 8 or 10 times its weight of water, or 

 by mixing the acid, also in a diluted state, with the solution of 

 sulphuret of barium. It requires 12 parts of water at 60, and 

 3 or 4 of boiling water for solution ; it is insoluble in alcohol. 



