PROFESSOR LETTS ON PHOSPHORUS-BETAINES. 331 
detected. One very carefully conducted experiment may be described to show 
how this was proved. 10 grms. of the product boiling between 304°-306°, were 
dissolved in water and mixed with excess of oxide of silver. Bromide of silver 
was precipitated, but no gas was evolved. The mixture of bromide and oxide 
of silver was then thoroughly squeezed from the solution in a cloth filter, 
suspended in water, and a current of sulphuretted hydrogen passed for some time 
until the mixture was thoroughly saturated. The aqueous solution was. then 
filtered off from the sulphide of silver, and was heated in a distilling flask. No 
acetic acid passed over. When hydrobromic acid of constant boiling-point 
began to distil, the residue was heated in a water bath and evaporated to dry- 
ness. A few flakes of crystalline matter (less than 0°5 grm.) remained. 
Neither acetate of silver then, nor any other salt of silver could have been 
precipitated with the bromide except in minute quantity. The aqueous solu- 
tion squeezed from the bromide of silver was heated in a distilling flask con- 
nected with an apparatus for collecting any gas that might be evolved, but none 
came off. Water at first distilled, and later 5-7 grms. of oxide of triethyl- 
phosphine boiling at 240°, and solidifying in the condenser. There remained 
in the distilling flask only a drop or two of a substance which was too small in 
quantity to be investigated. This experiment shows then, that when the 
product is acted on with oxide of silver, only bromide of silver and oxide of 
triethyl-phosphine are produced. 
The results of these experiments are decidedly antagonistic to the view that 
the volatile body consists of aceto-bromide of triethyl-phosphine, and in fact 
may be considered as proving that it is not that substance. They indicate, on 
the other hand, that it consists of a compound of hydrobromic acid with oxide 
of triethyl-phosphine. 
Crafts and Sitva* have investigated the action of hydrobromic acid 
on oxide of triethyl-phosphine. By heating the latter with a 64 per cent 
solution of the former to 110° C. they obtained a product which boiled at 
205°-210° C. under a pressure of 2 inches of mercury. This was redistilled 
under a pressure of 14 inch of mercury, and boiled at 198°-203° C. 
The author subjoins the results of the analyses of these two products, 
together with the mean of the numbers obtained by himself with the volatile 
product boiling at 303° C., and the numbers calculated for a compound of four 
molecules of oxide of triethyl-phosphine with three molecules of hydrobromic 
acid— 
Crafts’ and Silva’s product boiling at— The author’s Calculated for 
05 “2007 0 9822203". product. -4[P(C,H,),0],3HBr. 
Carbon, \/)\) “85:79 36:18 36°85 36:9 
Hydrogen,. . 8:03 8:23 8-05 ey 
Bromine, .  . 32:17 31:16 31:22 30°8 
* Journal of the Chemical Society, 1871, p. 637. 
