Deville and Caron on the Artificial Formation of Minerals. 277 



pertles with that produced from chloride of ethylene. By the 

 following experiment, however, acetal is formed from aldehyde. 

 Aldehyde is mixed with twice its volume of absolute alcohol and 

 saturated with hydrochloric acid gas ; two layers are formed — a 

 lower aqueous layer, and an upper one consisting of a compound 

 intermediate between acetal and chloride of aldehydene, its com- 



position being C^ H^ 010^=^4 JJs f 0'^ o^' acetal, ^4 g4/0S in 



CI C^H^O' 



which chlorine occupies the place of the group C'' H^ 0'^. It is 

 produced in accordance with the equation 



C4 H4 02 + C-* H6 02 + HCl = C8 H9 CIO2 + 2 HO. 



Aldehyde. Alcohol. New body. 



When this substance acts upon ethylate of soda, it gives rise 

 to chloride of sodium and acetal, 



C8H9C102 + C''H5Na02=NaCl+C'2H"'0''. 



Oxychloride of Sodium- Acetal. 



aldehydene. alcohol. 



The acetal obtained was found to have all the properties 

 attributed to it by Stas, its discoverer. 



Deville and Caron* have described a method by which they 

 have prepared several crystallized minerals. The method em- 

 ployed consists in the action of metallic fluorides on oxygen com- 

 pounds, either fixed or volatile. It requires a high temperature, 

 but is of very wide application, as the metallic fluorides are sel- 

 dom absolutely fixed. Corundum is prepared easily, and in large 

 crystals, by introducing into a carbon crucible fluoride of alumi- 

 nium, above which is fixed a small cupel of carbon filled with 

 boracic acid. The whole is fitted with a good cover, and kept 

 for an hour at a white heat. The vapour of the fluoride of alu- 

 minium meets that of the boracic acid ; and their mutual action 

 gives rise to fluoride of boron and to corundum, which is thus 

 frequently obtained in crystals a centimetre in length, but of no 

 great thickness, having the hardness and all the other physical 

 properties of the natural corundum. 



Rubies are similarly obtained, a little fluoride of chromium 

 being added to the fluoride of aluminium ; the operation is con- 

 ducted in crucibles of alumina, and the boracic acid placed in a 

 cupel of platinum. Blue sapphire and (/rcen corundum arc pro- 

 duced under similar circumstances, the difference in colour 

 arising from the difference in the quantity of chrome. Cymo- 

 phane, obtained by the action of boracic acid on fluoride of alu- 

 minium and glucinum, resembled the American specimens. 



• Comptes Rendus, April 1858. 



