292 PROFESSOR LETTS ON PHOSPHORUS-BETAINES. 
that it is necessary to cool the vessel containing the mixture in order to prevent 
loss. The resulting sulphine iodide is very similar to the iodide of a compound 
ammonium or phosphonium. Its hydrate is a powerful base which absorbs 
carbonic anhydride from the air, and precipitates the hydrates of metals from 
solutions of their salts. 
But there is one important particular in which a tertiary amine is utterly 
unlike a tertiary phosphine, or the sulphide of a hydrocarbon radical. <A 
tertiary amine is not capable of directly fixing oxygen, nor indeed of yield- 
ing any simple oxidised derivative. But both a tertiary phosphine and the 
sulphide of a hydrocarbon radical are oxidised with ease (indeed the former 
absorbs oxygen from the air with avidity), and simple products of oxidation 
are formed. Trimethyl-phosphine oxidises to (CH;),PO, and sulphide of 
methyl to (CH;),SO and (CH,),SO,. 
Dimethyl-sulphone (CH;),SO, and oxide of trimethyl-phosphine closely 
resemble each other. They are solid neutral substances which distil without 
decomposition. They resist the action of oxidising agents in a remarkable 
manner, being unchanged by boiling with nitric acid.* 
Dr Crum Brown and the author found that just as trimethyl-amine and 
trimethyl-phosphine combine with chloracetic acid to give the hydrochlorate 
of betaine, and of phosphorus-betaine respectively, 
Cl 
cl 
(CH) =N— and (CH,)=P 
CH,—COOH, 
NCH,— COOH 
sulphide of methyl combines with bromacetic acid to give the hydrobromate 
of a body which they called thetine, or rather dimethyl-thetine, 
as it 
ene. ort COOH. 
Thetine is, in certain respects, analogous to betaine. Both are deliques- 
cent bodies, possessing a neutral reaction, and only weak alkaline properties, 
and both yield similar salts, which are readily obtained by the action of silver 
salts on their hydrochlorates or hydrobromates. 
But the author has shown that both the base thetine and also its salts, are 
decomposed by heat in a simple and characteristic manner, whilst Briwu has 
investigated the action of heat on salts of betaine, and has found that they 
decompose in a completely different way. 
These results of Briuw’s, coupled with the author’s experiments, led to the 
question, How will the salts of phosphorus betaine behave when heated ? and 
* The author has seen their vapour pass almost unchanged over a layer of mixed carbonate and 
nitrate of potash, heated to incipient fusion. 
