122 Journal of the Mitchell Society [Februanj 



colloid and the liberation of the acid, e. g., ZrCl«+H20=ZrOCl2+ 

 2HC1; 2ZrOCl2+2H20=ZrO(OH)..ZrOCl2+2HCl. Where several 

 molecules of ZrOCU are hydrolyzed at one step more complex prod- 

 ucts will result. This method of writing the formulas has therefore 

 been adopted throughout this text wherever accurate knowledge of 

 the composition of the substance was available. 



The tetrahalides of zirconium, especially the tetrachloride, form 

 a number of substitution compounds with organic substances. In 

 these all or half of the chlorine may be substituted. Thus acetic 

 acid and its homologues of the aliphatic series give compounds Zr 

 (C2H302)4, or in general, Zrll4, whereas benzoic acid and its homol- 

 ogues give ZrCLCCeH 6.002)2 or ZrCURs. With the esters, ketones, 

 and aldehydes addition compounds are formed. Thus for the ben- 

 zoic ethyl ester compound the formula is ZrCl4(C6H6.C02.C 2115)2. 

 Similar direct addition compounds are formed betw^een ZrCh and the 

 amines, the pyridin bases, etc. The tetrachloride has been suggested 

 as a catalyzing agent in organic synthesis by Fridel and Crafts. 



Chapel Hill, N. C. 



