34 Dr. N. Collie on the Action of Heat on 



silver was removed by sulphuretted hydrogen, and the acid 

 solution was then carefully neutralized with a small quantity 

 of the hydrate of triethylbenzylphosphonium. On concen- 

 trating this solution by evaporation on a water-bath, a small 

 amount of decomposition was noticed, a trace of a free tertiary 

 phosphine being produced, and, what seemed remarkable, the 

 phosphine was not the triethylphosphine but the diethyl- 

 benzylphosphine, which possesses a very different smell from 

 the triethylphosphine, and can therefore by this property be 

 easily distinguished from it. The solution, as it became con- 

 centrated, was distinctly acid to litmus-paper, and was there- 

 fore further concentrated by allowing it to stand over sulphuric 

 acid in vacuo. The syrup eventually solidified to a mass of 

 deliquescent crystals. 



These were transferred to a distilling-flask, and heated ; 

 they soon fused : decomposition began at about 230° C, and 

 then proceeded rapidly. A gas was evolved which was 

 recognized as sulphur dioxide by its smell, solubility in 

 water, and other properties. The distillate was partly cry- 

 stalline, and also smelt strongly of sulphur dioxide ; it was 

 treated with water (in which the crystals were insoluble) and 

 warmed, in order to volatilize the sulphur dioxide and traces 

 of toluene, which were also noticed. The crystals were 

 eventually separated from the aqueous solution, which con- 

 tained only the oxide of triethylphosphine, and, after washing 

 with water and recrystallizing several times from hot dilute 

 alcohol, they were obtained as white glistening leaflets : 

 m.p. 119° C. (0*111 grm. substance gave 0*381 C0 2 and 

 0*0666 H 2 0. C = 93*61 per cent., H = 6*66 percent. Stilbene, 

 C U H ]2 , contains = 93*33 per cent, and H = 6*66 per cent.) 

 The melting-point of stilbene is given as 124° C, and this 

 hydrocarbon unites directly with bromine, giving a dibrom- 

 stilbene, m.p. 237° C. Some of the crystals, m.p. 119° C, 

 were accordingly treated with bromine ; a slightly yellow 

 crystalline compound was obtained, which, when heated to 

 230° C, grew brown and half melted, but did not melt com- 

 pletely till the temperature had risen to 240° C. There is 

 little doubt, therefore, that the hydrocarbon is stilbene. 



The mother liquors, from which the stilbene was obtained, 

 yielded on evaporation another crystalline substance, which 

 possessed a much lower melting-point, and seemed from its 

 appearance to be dibenzyl, as it melted at b > 0°-63° C, con- 

 tained neither phosphorus nor sulphur, and burnt with a very 

 smoky flame. It was unfortunately present only in very 

 small quantities; and, although several attempts were made to 

 isolate it in a state of purity, they were without success. 



