1888-89.] Prof. Letts and R. Blake on Dibenzyl-PAosphine. 195 
of general application. It is extremely simple, though somewhat 
tedious in carrying out.* It consists in making an ordinary com- 
bustion of the substance with pure oxide of copper, and afterwards 
dissolving the contents of the combustion tube in nitric acid, and 
determining the phosphorus with molybdate of ammonia, &e. 
Applying this method to the analysis of the supposed dibenzyl- 
phosphine, we obtained the following results (IV. and V.). 
We give at the same time the determinations of phosphorus made 
both by Hofmann (I.) (by a method not described), and by one of us 
and W. Wheeler (II. and HI.), in the same substance (by burning 
with lime in a stream of oxygen) : — 
I. II. III. IV. V. 
Phosphorus:— 13*6 14*35 15*00 9*86 9*98 
I. Hofmann. 
II. and III. Letts and Wheeler. 
IV. and V. Letts and Blake. 
3. The following compounds of Hofmann’s body were prepared 
and analysed f : — 
Bromide . — Obtained by adding bromine to a solution of the body 
in glacial acetic acid. It crystallises usually in yellow needles. It 
is unstable, and loses bromine when boiled with water or glacial 
acetic acid, and possibly on drying also. 
Prepared from 
Hofmann’s Dibenzyl-Phosphine. 
Obtained : 
“ {rinat iontl 2 ” 
Carbon, 
Hydrogen, 
56*4, 56*5, 56*5 
5*31, 5*57, 5*04 
Calculated: {(C 7 H 7 ) 2 HP} 2 Br 2 
Bromine, 27*2 
Carbon, 57*1 
Hydrogen, 5*1 
Oxide of Tribenzyl-Phosphine. 
28*4 
56*9 
4*9 
7(C 7 H 7 ) 3 P0.5Br 2 
26*31 
58*00 
4*83 
5(C 7 H 7 ) 3 P0.4Br 2 
28*5 
56*3 
4*7 
* Details of this method will be given in another paper. 
+ It will be seen that a formula can be devised in every case, both for a com- 
pound of (C 7 H 7 ) 2 HP and (C 7 H 7 ) 3 P0, which corresponds with the results obtained; 
and it is remarkable how closely most of the results obtained agree with those 
required for a compound of the former. We also give in some cases the 
analyses of compounds prepared in a similar manner with what was known to 
be the oxide of tribenzyl-phosphine. Most of the compounds are unstable, 
and their composition often varies according to the method or conditions 
employed in their preparation. 
