M. GUINARD ON DISINTEGRATION OF DIATOMACEOUS DEPOSITS. 189 



but I have found six successive operations necessary to obtain a 

 good result. 



There only remains now to add water in excess to re-dissolve the 

 crystallized salt, to empty the whole into a suitable vessel, and to 

 add a large quantity of water. 



This method has been communicated by M. Parmentier, Pro- 

 fessor of Chemistry to our faculty of science, who has occupied 

 himself specially with the phenomena of the supersaturation of 

 salts. 



Another substance which may be found serviceable, and which is 

 used in the arts to detect stones cracked by frost, is hyposulphite 

 of soda, but the manipulation is more delicate. However, I 

 indicate the process here, but give the preference to the acetate of 

 soda process. 



Hyposulphite of soda melts in its water of crystallization ; put 

 this salt into a capsule, heat it in a water bath to 48°, the salt will 

 deliquesce. Plunge therein the deposit before heating, and when 

 the solution shall be liquified and re-cooled add a small crystal of 

 hyposulphite of soda, re-crystallization will take place, and the 

 deposit will be disintegrated ; re-melt again and add water in 

 excess, then decant. It will be understood that this operation 

 must be repented if success is not at once obtained. 



