146 Mr. Rainey on the formation of [Mar. 30, 



to become gradually disintegrated, and replaced by an entirely different set 

 of crystals, consisting of oxalate of lime and chloride of calcium. In this 

 experiment, either the oxalate made artificially, or that obtained from any 

 natural source, may be employed ; but the strength of the solution of the 

 chloride of calcium must not be less than that of a mixture consisting of 

 equal parts by measure of a solution of this chloride saturated at a tem- 

 perature of 60 Fahr. and water. The time required for the disintegra- 

 tion of all the oxalate of lime and its combination with the chloride of 

 calcium to form crystals of the double compound of these salts, depends 

 upon the size of the crystals of oxalate of lime employed in the experi- 

 ment : if they are very small, or if the oxalate is to all appearance amor- 

 phous, evidence of these changes will be visible in a few hours, and the 

 crystals completely formed in a few days ; whilst if the oxalate crystals are 

 large and well formed, some weeks will elapse before they have entirely 

 disappeared and become replaced by the new crystals. 



These changes are also influenced by the strength of the solution of the 

 chloride of calcium : if it be fully saturated, they take place more quickly, 

 but the crystals will be small ; if diluted, they will, on the contrary, be 

 produced more slowly, and the crystals will be larger and better defined, 

 (fig. 2.) Crystals of oxalate of magnesia put into a cell with a saturated 



Fig. 2. 



solution of chloride of magnesium undergo similar changes, a double salt, 

 consisting of oxalate of magnesia and chloride of magnesium, being formed. 

 In this case the changes take place very slowly, several months being re- 

 quired for the formation of perfect crystals. These crystals have their 

 sides and angles exceedingly sharp and well defined (fig. 3). Lastly, the 

 oxalate of baryta, and a saturated solution of the chloride of barium placed 

 under the conditions above mentioned, yield the same results, and crystals 

 of oxalate of baryta and chloride of barium are formed (fig. 4.) 



The series of facts requiring notice in the process of formation of these 



