92 



fully acid ur alkaline reaction, because diphenyl methane is then also 

 formed. 



As solvent we selected in all cases a liquid containing 80 7o 

 ethyl alcohol to which the acid, alkali, etc. was eventually added. 



In 80 7o alcohol benzophenone is practically insoluble whilst the 

 hydrole is readily soluble therein, so that the determination of the 

 two substances in a mixture is a simple matter. 



Solubility of pinacone : Shaken in a thermostat for one day at 25°. 



In supersaturated solution 100 cc. retained 0.124 gram. 



,, unsaturated ,, ,, ,, dissolved 0.110 „ 



The solubility of benzhydrole = d= 35 grams. 



We have also ascertained that the solubility of jjinacone is not 

 appreciably influenced by quantities of hydrole uj) to 5 grams. 



The modus operandi was very simple. Quantities of 5 grams of 

 benzophenone were boiled for some time in a reflux apparatus, with 

 the requisite amounts of the reduction agent, in 50 cc. of 80 7o 

 alcohol; the solution was filtered hot, the residue was extracted with 

 small quantities of boiling 807o alcohol, the filtrate made up to 

 100 cc. and then shaken at 25° for one day. 



In 50 cc. of the solution the hydrole was determined by evaporation. 

 The residue was t.ested as to its purity by the determination of its 

 odour, melting point, and crystal-habit. 



This evaporation was always carried out in the same manner, for 

 the hydrole is somewhat volatile; for instance, if the evaporation 

 lasts 50 minutes, 12 mg. of benzhydrole get lost. 



For this loss a correction was made as well as for the pinacone 

 eventually present. 



2. Reduction in a neutral medium. 



This was only possible with aluminium amalgam. This was 

 prepared by shaking aluminium grit with 17o HgCl2 solution for 

 15 minutes at the ordinary temperature, filtering off rapidly and 

 washing with 96 7o alkohol. It was then at once used for the 

 reduction in the proportion of 10 grams of the aluminium to 5 grams 

 of benzophenone. 



The following figures were obtained: (see table page 93). 



Hence, the result shows that the proportion in which hydrole 

 and pinacone are formed is constant, namely 68 7o '• 327o. indepen- 

 dent of the time of the reduction. 



Pinacone once formed is not reduced any further in a neutral 

 solution within seven hours, so it cannot be considered as an inter- 

 mediate product. 



