of Mineral Substances. 273 



100 parts were heated in a covered crucible ; it decrepitated 

 into a coarse powder, losing 5 per cent, of weight, but remain- 

 ing white. The heat was increased to redness, when it lost 11 

 percent., and became of a blackish-grey colour. 



B 

 Digested in cold and moderately strong nitric acid, it dis- 

 solved slowly, and with sparing effervescence, forming a tran- 

 sparent straw-coloured solution. If the acid be heated, it 

 effervesces strongly forming a reddish-brown solution, and the 

 undissolved portion of the fossil appears orange-yellow ; 

 when perfectly dissolved, the colour of the solution is pale 

 reddish brown. 



C. 



100 grains of the coarsely-powdered mineral were dissolved 

 in nitric acid, and the solution neutralized by caustic ammonia. 

 A brown flocculent precipitate fell, weighing, when dry, 14 

 grains ; this was re-dissolved in nitro-muriatic acid, the excess 

 of acid was then neutralized by soda, and the iron separated 

 by succinate of ammonia. The succinate of iron yielded, after 

 ignition, 5.5 grains of magnetic oxide of iron. But, since 

 the iron exists in this mineral in the state of carbonate, the 

 above result must be assumed to indicate 7.5 grains of carbo- 

 nate of iron. The liquid from which the iron had been thrown 

 down was heated to its boiling point, and mixed with carbonate 

 of soda, which gave a white precipitate, becoming black when 

 heated, and weighing, after ignition, 4 grains. Digested in nitric 

 acid, the greater portion of this precipitate was dissolved, but 

 there remained a black residue, consisting of oxide of manga- 

 nese, and weighing 1.25 grains, which I consider as equal to 2 

 grains of carbonate of manganese. Carbonate of soda threw 

 down from the remaining nitric solution 3.5 grains of carbonate 

 of mufjnesia 



b. The excess of ammonia, in the original solution a, was 

 huporsaturated by nitric acid, and carbonate of soda added to 

 the cold solution as long as it occasioned a precipitate, wiiicii. 



