PROFESSOR LETTS ON PHOSPHORUS-BETAINES. 29 
aware that any phosphorus compound analogous to an amide has been obtained. 
Phosphorus indeed displays but little tendency to combine with oxidised hydro- 
carbon radicals. | } 
If we compare the phosphines with mercaptans and hydrocarbon sulphides, 
on the one hand, and with the amines, on the other, we find (as might indeed be 
expected) very much the same difference between them as we notice between 
phosphuretted hydrogen, sulphuretted hydrogen, aud ammonia. 
Thus compounds of primary phosphines with the hydracids are decomposed 
by water, just as phosphonium iodide is decomposed by water, and the phos- 
phines oxidise with the greatest ease, and even spontaneously. The products of 
their oxidation are analogous to those which the mercaptans and hydrocarbon 
sulphides yield. Thus— 
RSH gives R’SO,(OH) 
Beas a aes. 
REE, , RPO(OH), 
R,PH ,, R,PO(OH), 
nee POS 
as the final products of oxidation. 
The most characteristic property of a mercaptan is the readiness with 
which it exchanges its hydrogen for metals. The author is not aware that 
any attempts have been made to obtain analogous metallic derivatives of 
primary and secondary phosphines, but it is highly probable that such bodies 
may exist and could be easily obtained. 
The organic compounds of the three elements which best admit of com- 
parison are the tertiary amines and phosphines and the sulphides of hydro- 
carbon radicals. These bodies have been well studied, and all of their most 
important properties are known. Let us compare the properties of (CH;),N 
with those of (CH;),P and (CH;),S. They are all volatile liquids of peculiar 
and characteristic odour, and all possess alkaline properties. These are most 
strongly marked in trimethyl-amine, least so in sulphide of methyl. 
Perhaps the most characteristic property of a tertiary amine is the readiness 
with which it combines with the iodide of a hydrocarbon radical to form the 
iodide of a compound ammonium, the hydrate of which is a very powerful base. 
A tertiary phosphine is perfectly similar in this respect, as it combines with 
great readiness with an iodide of a hydrocarbon radical, and from the product of 
union, salts of the compound phosphonium are easily obtained, analogous in a 
great many respects to those of the compound ammonium. A sulphide of 
a hydrocarbon radical also combines readily with the iodide of a hydro- 
carbon radical. Thus on simply mixing sulphide and iodide of methyl, a 
reaction at once occurs, and so much heat is developed by their combination 
