963 



If llic latter is tlic case, the pinacoties belonging to tlie ketones 

 vvliic'h, in a iiciili-al or vcvy faint Iv alkaline medium, gi\e nnicli 

 hydrole must be (,leeom|)oso(l l)y alkalis iuto a mixtui-e of liydn)le and 

 ketone nuicli more i'a])i(lly tlian those which in the same circum- 

 stances yield but little hydi'olc. 



It may even l)e expected that the formation of hydrole and the 

 splitting of the pinacone by alkalis will proceed in a strongly 

 parallel manner. 



This has now indeed proved to be the case. The greater the 

 decomposition velocity of the pinacone by alkalis, the smaller the 

 quantities formed in the reiluction with aluminium auialgam. 



With this is also , proved that at the l)Oundary layer of the amalgam 

 is present an excess of OlI-jous which is only accessible to the pinacone 

 in its nascent state. If, for instance, pinacone is exposed to the action 

 of aluminium amalgam and 807u^'<-'o'i<^'- i^ i"^ P^''^t'b<^*^".V "ot attacked, 

 moreover the [troportion in which pinacone and hydrole are formed 

 is nearly independent of the duration of the reduction. (1*^ commu- 

 nication p. y2). 



The proportioJi of the (piantities of pinacone and benzhydrole in 

 which these are formed during the reduction of thirteen aromatic 

 ketones with aluminium amalgam has been given in the J"*' com- 

 munication p. 98. 



The decomi)osition velocity of the pinacones was determined by 

 dissolving quantities of 0.5 gram in a mixture of 75 cc. of ether 

 and 5 cc. of alcohol diluting this solution to J 05 cc. with alcoholic 

 solutions of potassium hydroxide of iV/0.42, .V/0.042 and A^O.0042 

 strength, respectively. The normalities of the solution thus become 

 0.1, O.OJ, and 0.001. 



These mixtures were kept for detinite periods at 25°, then diluted 

 with cold water, agitated a few times with ether, the ethereal solution 

 was evai)Orated down rapidly and the residue digested with 807o 

 alcohol at 25° in the manner described previously (I. c. p. 9) in 

 order to get to know the quantities of undecom|)Osed [linacone. 



The subjoined table and graphic representations give a survey of 

 the results obtiiined. 



The luimbers of the lines in the graphic representations appertain 

 to the numbers with which the i)inacones are indicated in the table ; 

 the percentages next to or below those numbers in the graphic 

 representation indicate the quantities of pinacone formed from the 

 respective ketones by reduction with alumiiuim amalgam in HOy» alcohol. 



From the graphic representation of the pinacone deconq)osiliou, 

 where, as observed above, are indicated the percentages of pinacone 



