of Mineral Substances. 275 



Analysis of Anhydrite. 

 A. 



A fragment of blue anhydrite (from Sulz on the Neckar) 

 weighing 300 grains, Avas kept red hot in a platinum crucible 

 for half an hour ; it became soft and yellowish-white, but lost 

 no weight. 



B. 

 Thirty grains of the powdered mineral were boiled in 12 

 ounces of water ; 8 grains were dissolved, but the solution did 

 not render nitrate of silver in the least turbid, so that it con- 

 tained no muriatic acid. 



C. 



a. 200 grains of pulverized anhydrite were boiled with 400 

 grains of carbonate of potassa in 8 ounces of water for a quarter 

 of an hour. The alcaline liquor was then filtered off, neutralized 

 by muriatic acid, and mixed with muriate of baryta as long as 

 a precipitate was produced . The dry sulphate of baryta weighed 

 345 grains = 114 grains of dry sulphuric acid. 



b. The residue upon the filtre dissolved with effervescence in 

 dilute nitric acid, excepting 0.5 grain of silica ; supersaturated 

 with caustic ammonia the solution gave no precipitate ; it was 

 therefore again rendered neutral by nitric acid, and tested with 

 prussiate of potassa, and after a while it deposited a small por- 

 tion of Prussian blue indicating not more than 0.20 grain of 

 oxide of iron. 



c. This being separated the solution was saturated whilst 

 boiling hot, with carbonate of potassa; carbonate of lime was 

 thus thrown down, weighing when washed and dried in a gentle 

 heat, 153 grains = 84 grains of lime. This carbonate was then 

 neutralized with sulphuric acid, evaporated to dryness, and ig- 

 nited; it thus afibrded 198 grains of regenerated sulphate of lime. 



100 parts therefore of this blue anhydrite were resolved into 



Lime 42. 



Sulphuric acid 57. 



Oxide of iron 0.10 



Silica (probably adventitious) . , 0.25 



99.35 



