184 Drs. Letts and Collie on the Salts of 



not very satisfactory, owing to the tendency of the benzyl 

 radical to split into hydrocarbons at the high temperature at 

 which the decomposition occurred. 



We thought it probable that the salts of tetrethylphospho- 

 nium would decompose at a lower temperature, and would 

 therefore be better suited for investigation. Several of the 

 salts of tetrethylphosphonium which we investigated had 

 already been described by Hofmann * ; one or two, however, 

 we prepared for the first time. 



Preparation of Iodide of Tetrethylphosphonium. 



As this salt was the starting-point for the preparation of 

 the other compounds of the phosphonium, we devoted con- 

 siderable care to its manufacture in the pure state. 



When triethylphosphine is added to iodide of ethyl, the two 

 combine rather suddenly and with considerable evolution of 

 heat, so that unless care is exercised loss of material may easily 

 occur. Hofmann suggests that the iodide of ethyl should be 

 diluted with ether before the addition of the phosphine, and 

 at first we acted on this suggestion ; but subsequently we 

 found that, by carefully cooling the mixture and using excess 

 of iodide of ethyl, the reaction could be kept completely under 

 control, and that the addition of ether was unnecessary. The 

 first quantity of the phosphonium iodide was prepared in 

 etherial solution : 30 grms. of triethylphosphine were added 

 to a mixture of 43 grms. of pure iodide of ethyl and 500 

 grms. of ether. The mixture was left for a night, when 30 

 grms. of feathery white crystals separated. These were 

 washed with dry ether, and dried in vacuo over sulphuric 

 acid ; the determination of iodine in them was made volume- 

 trically. 



# 600 grm. required 21*9 cubic centim. decinormal nitrate 

 of silver solution = 0*27813 grm. iodine = 46*36 per cent. 



From the ether mother liquors a further batch of crystals 

 was obtained. 



The next quantity of the phosphonium iodide was prepared 

 by the direct addition of 30 grms. of triethylphosphine to a 

 large excess (200 grms.) of iodide of ethyl, which was con- 

 tained in a flask, fitted with an upright condenser and placed 

 in water. After a short time violent ebullition occurred, and 

 a considerable quantity of iodide of ethyl volatilized into the 

 condenser. On distilling off the excess of this from a water 

 bath, a snow-white mass of crystals remained. 



These were recrystallized by dissolving them in alcohol and 

 precipitating with ether. A determination of iodine in the 

 * Hofmann and Cahours, Annalen, vol. civ. p. 1. 



