( 239 ) 



The result was that was dissolved: 



from the finest calcite powder: 4,— milligrams 



and 4,1 ,, 



from the finest aragonite powder: 5,4 ,, 



and 5,7 ,, 



The quantities of dissolved mineral are very small and so the 

 inaccuracies of the weighing have a great influence. Though these 

 numbers cannot have an absolute validity, 1 hold myself authorized 

 to say, that an important difference in solubility does not exist. 

 Spoken practically calcite and aragonite are bolh nearly insoluble in 

 pure water. The number found for calcite agrees sufficiently with 

 the knowledge that 10000 parts of pure water dissolve 0,2 or 0.25 

 parts of calcite. 



B. Solubility of calcite and aragonite in water containing carbonic 

 acid. 



The solubility in water containing carbonic acid in the form of 

 bicarbonate depends on the duration of the action and on the strength 

 of the dissolving liquor or on the quantity of carbonic acid. I always 

 prepared the liquor immediately before adding the mineral powder, 

 by leading through 200 cM s of distilled water a slow current of 

 pure carbonic acid during twenty minutes and by closing the glasses 

 during the experiment. So the strength of the liquor may always 

 have been the same. 



I obtained the result that 200 cM 3 of water containing carbonic 

 acid had dissolved after one week : 



from the coarse calcite powder: 54,7 milligrams 



from the coarse aragonite powder: 61,8 milligrams 



The same quantity of the liquor had dissolved after two weeks: 



from the calcite powder: 76,5 milligrams 



from the aragonite powder: 86,2 milligrams 



and after tour weeks: 



from the calcite powder: ION, 4 milligrams 



from the aragonite powder: 122.4 milligrams 

 Kor the same reason as is mentioned sul» A, a second series of 

 experiments was made with the finest powder of the two minerals. 

 200 cm', of water containing carbonic acid had dissolved after 

 one week : 



from the finest calcite powder: 267,8 milligrams 



from the finest aragonite powder: 332,8 milligrams 

 From these numbers I conclude: 

 1. that indeed aragonite is dissolved << little faster by water con- 



