﻿972 Mr. J. Kendall on the Solubility of 



at the temperatures of 25° C., 50° C, and 100° C, and results 

 are given below in grammes per litre. 



Prepared Carbonate. 



25 C Mean result. 



2 days -014451 '014541 



3 days -01436/ -01444 j -01445 



50° C. 



2 days -015101 -015261 



3 days -01521 J -01503/ -01515 



100° 0. 



60 mins -01824 



lOOmins -01809 '01816 "01816 



Soft Chalk. 



100° c. 



60 mins (-02117) '01784 



100 mins -01769 ... -01777 



It will be seen that the figures are the same as for calcite. 

 The experiments with soft chalk were carried out by treating 

 a quantity with successive portions of water — the first high 

 value is due to the removal of impurities. 



The amorphous form is hence seen to be extremely un- 

 stable, and no figures for its solubility can be obtained. 

 Another method of preparation — heating the precipitated 

 oxalate to oxide and converting to carbonate by slowly 

 cooling in a current of carbon dioxide — led to the same 

 solubility values being obtained. Conversion to calcite takes 

 place either as soon as the carbonate is formed at the high tem- 

 perature, or else as soon as it is brought in contact with water. 

 The powdered substance shows, under the microscope, no 

 signs of crystalline character ; its density is, however, the 

 same as that of calcite (2*70 by the Westphal balance). For 

 this reason no change in volume could be observed when a 

 dilatometer was packed with the powder and water drawn in 

 to fill the bulb. 



Solubility under Atmospheric Conditions. 



The extremely small proportion of carbon dioxide in 

 ordinary air is sufficient to raise the solubility of calcium 

 carbonate at the ordinary temperature several hundred per 

 cent. It is therefore necessary to know accurately the 

 amount of carbon dioxide in the air at the time of experiment 

 to render the results, which are of special importance for their 

 applications to water analysis and geology, of any value. 



