BENZYL PHOSPHINES AND THEIR DERIVATIVES. 533 



The amount of oxygen absorbed by the phosphine decreasing in a regular manner as 

 the series is ascended. 



The oxides of tertiary phosphines are solid substances of remarkable stability. They 

 can in the majority of cases be distilled, and even boiled with nitric acid without change. 

 By no means as yet discovered can they be reduced. Hydracids combine with them, 

 and they give crystalline compounds, with a number of metallic salts, such as the chlorides 

 of platinum, zinc, mercury, iron, cobalt, &c, also in some cases with chloride of acetyl, 

 bromine, and sulphur. 



Tertiary phosphines also combine with the elements of the sulphur group, forming 

 compounds analogous to the oxides. 



The salts of tertiary phosphines are readily obtained by dissolving the bases in acids. 

 They are stable, and are not, as a rule, decomposed by water. Their compounds with 

 hydracids have been chiefly studied; those containing oxyacids have not been investi- 

 gated (with very few exceptions). The haloid salts dissociate to a greater or less extent 

 on heating. Their hydrochlorates combine with chloride of platinum to give chloro- 

 platinates of normal composition. 



Some of the tertiary phosphines combine with chloracetic acid to give hydrochlorates 

 of phosphorised betaines. At present only two or three of these substances have been 

 obtained — tri-methyl phosphorus betaine by Meyer,* the corresponding ethyl derivative 

 by HoFMANN,t and in addition to these two the closely allied compound, tri-methyl phos- 

 phorus benzo-betaine hydrochlorate, by Michaelis and Czimatis,| 



(CH 3 ) 3 PV^_ COOH . 



The compounds of these phosphorised betaines are stable and well-defined substances. 

 One of us§ has investigated the reactions and decompositions of the ethylated body, 

 which are of some interest. 



The hydrate and the salts of this betaine lose carbonic anhydride when heated, and 

 give rise to the hydrate or salt of methyl-tri-ethyl-phosphonium, 



(C 2 H 5 ) 3 P< CH2 _ COOH = C0 2 + (C 2 H 5 ) 3 P<^ CH ^ 



a reaction which is entirely analogous to that occurring when the corresponding 

 sulphur compounds (thetines) are heated, 



(CH 3 ) 2 S^ CH2 _ COOH =C0 2 + (CH 3 ) 2 S^ CH3 



While it is perfectly different from that which the true (nitrogen) betaines experience, as 

 they either dissociate into the original trialkyl-amine and the group X - CH 2 — COOH 

 (or the products of its decomposition), or distil unchanged. || 



* Meyer, Berichte, iv. (1871) p. 734. + Hofmann, Proc. Boy. Soc, xi. p. 530. 



X Michaelis and Czimatis, Berichte, xv. (1882) p. 2018. § Letts, these Transactions, xxx. part 1, p. 285. 



|| Bruhl, Annalen, 177, p. 214. 



