DR. A. W. HOFMANN ON THE PHOSPHORUS-BASES. 
455 
only part of the bromine. When the liquid filtered from the precipitated bromide of 
silver was mixed with carbonate of sodium, to remove the excess of silver, and evaporated, 
the residue, when ignited with lime and dissolved in nitric acid, gave, on addition of 
nitrate of silver, a fresh quantity of bromide of silver. I therefore endeavoured to 
obtain the entire quantity of bromine by means of recently precipitated oxide of silver, 
a process which I had previously found serviceable in similar cases. The result con- 
firmed my anticipation. Digestion with oxide of silver removes the whole of the 
bromine, and shows that the quantity precipitated by nitrate of silver is only half the 
total amount. 
III. l’8445grm. of bromide digested with oxide of silver, gave, after the removal of 
the excess of oxide of silver by nitric acid, 2'2635 grm. of bromide of silver. 
These numbers lead to the formula 
^8 ^19 P 
as seen from the following comparison : — 
Theory. 
A 
Cs 
96 
31-37 
Hi, 
19 
6-21 
P 
31 
10-14 
Br 
80 
26-14 
Br 
80 
26-14 
306 
100-00 
Experiment. 
r ^ 
I. II. III. 
31-59 
6-26 
25-94 
52-22 
The interpretation of these results presents no difiiculty. The crystals are evidently 
the bromide of a monophosphonium in which 3 equivs. of ethyl are substituted for 
3 equivs. of hydrogen, the last equivalent of hydrogen being replaced by a secondary 
radical, C 2 H 4 Br, which for the present I will call monobrominated ethyl or bromethyl. 
The molecular formula 
[(C2H4Br)(C2Hj3P]Br 
represents the constitution of this salt. 
I have already observed that this bromide is occasionally obtained in well-defined 
crystals. They were examined by Quintixo Sella, who has sent me the following 
description : — 
“ System monometric (regular). 
The crystals exhibit the form of the rhombic dodecahedron 110 (Fig. 28). They 
are sometimes elongated so as to present the aspect of dimetric crystals, as in Fig. 29. 
Sometimes it even happens that one of the faces 1 1 0 is much more developed than the 
parallel face 110 (Fig. 30), so that scarcely more than half the crystal (Fig. 29) appears 
to exist. Sometimes the faces exhibit strise parallel to the adjacent edges of the rhombic- 
dodecahedron. 
