356 M. Arfvvedsou's Examination oj certain Minerals. 



washed with boUing water. It was again dissolved in muriatic 

 acid and caustic potassa added to excess : the precipitate be- 

 came redissolved, and left oxide of iron behind, which, after 

 exposure to a red-heat, weighed 0,067. On redissolving it in 

 muriatic acid, it was found to contain 0,007 gram, (b) of 

 silica; thus there remained 0,06 [c) for the oxide of iron. 

 The alumina was separated from the alkaline fluid by mu- 

 riatic acid and carbonate of ammonia, and weighed 0,321 

 gram. This also left, after solution in sulphuric acid, 0,007 

 gram. (J) of silica. The quantity of alumina was therefore 

 0,314 gramm. {e) 



The fluid, precipitated with caustic ammonia, and then com- 

 pletely neutralized by a few drops of muriatic acid, was treated 

 with oxalate of ammonia, which separated oxalate of lime. 

 This was well washed with warm watei", exj^osed to a red-heat, 

 mixed with a little carbonate of ammonia, and gently heated 

 in order to drive off" the excess of ammonia; in this manner 

 0,920 gram, of carbonate of lime were obtained, equivalent to 

 0,518 of pure lime {/). 



The liquid, freed from lime, was mixed with a suflficient 

 portion of subcarbonate of potassa, and evaporated to dryness. 

 This dried mass, after solution in water, left a substance be- 

 hind, which, after being ignited, weighed 0,006 gram, and, 

 upon trial, proved to be oxide of manganese with a trace of mag- 

 nesia (o-). 



A portion of this fossil coarsely powdered, and exposed to 

 a red-heat in a platinum crucible, suffered no loss of weight. 



This fossil has therefore yielded, 



Silica [a) 0,625 



(^) 0,007 In 100 Parts. Oxygen. 



[d] 0,007 0,639 41,87 21,06 



Alumina (^) 0,314 20,57 9,06 



Lime (/) 0,518 33,94 9,53 



Oxide of iron (c) 0,060 3,93 1,20 



Oxide of Mangranese, 1 



and Magnesk | ^'006 0,39 



1,537 100,70 



From this it appears, that the proportion of oxygen in the 

 silica is equal to that of the bases taken together ; and that, 

 besides this, the quantity of oxygen in the alumina and in the 

 lime is equal ; and is, in each of these bases, eight times as 

 great as in the protoxide of iron. The formula, therefore, 

 which expresses the composition of this fossil will stand thus, 



FS f 



