DE. A. W. HOFMANN ON THE PHOSPHOEUS-BASES. 
m 
The percentages corresponding to these analytical numbers are exactly those of the 
platinum-salt of the ethylene-diphosphonium. 
C,,H3,P2Pt,Clg = 
(C 2 H 4 ) 
L 
.(C2H,)3P^ 
(C,H3)3P 
Cl2,2Pt Cl,. 
Theory. 
vV 
Experiment. 
A 
r 
( 
I. 
II. 
III. 
Cu 
168 
24-91 
24-85 
H 34 
34 
5-05 
4-93 
P 2 
62 
9-19 
— 
Pt, 
197-4 
29-27 
29-23 
29-01 
Clg 
213 
31-58 
674-4 
100-00 
Nevertheless the two substances are not identical. In addition to the difference in the 
physical properties and in the behaviour with dilute hydrochloric acid, the two salts exhi- 
bit other well-defined marks of distinction. The crystalline salt is perfectly insoluble in 
water, even when boiling. The amorphous salt dissolves readily, and is deposited again 
on cooling in the same amorphous condition. In designating this peculiar molecular 
variety as paradiphosphonium-compound, I simply wish to distinguish it from the salt 
of the ordinary diphosphonium, without giving any opinion respecting the nature of the 
difference. The existence of the diphosphonium-compounds in the crystalline and in the 
amorphous condition, reminds us of the behaviour of some of the native organic bases 
under the influence of heat. It is well kno^vn that several of these substances, which 
are remarkable for their powers of crystallization, are rendered perfectly amorphous 
when heated for some time above their melting-point. 
As might have been expected, the paradiphosphonium -compounds are slowly and 
gradually reconverted into the ordinary diphosphonium-salts *. 
The hydrated paradiphosphonium, when separated from the platinum -compound 
by successive treatment with sulphuretted hydrogen and oxide of silver, yields with 
hydriodic acid a gummy mass which only gradually assumes the crystalline form. By 
a considerable number of recrystallizations, the characteristic di-iodide was ultimately 
obtained with all its properties ; when converted, by treatment, with chloride of silver, 
into the dichloride, and precipitated by dichloride of platinum, it immediately yielded 
the well-known crystalline precipitate so frequently mentioned in this paper. In order 
to fix by numbers this transition, and more especially the formation of diphosphonium- 
compounds by the action of bromide of vinyl upon triethylphosphine, the soluble bromide 
obtained in the reaction between the two last-named bodies was successively treated with 
oxide of silver and hydriodic acid. The iodide, after numerous crystallizations from 
alcohol, gave on analysis the following numbers : — 
* In several experiments, tlie reaction between bromide of vinyl and triethylpliospbiue gave rise to the 
foripation of a mixture of the amorphous and crystalline dipbospbonium-compouuds. 
3 T 2 
