82 Proceedings of Royal Society of Edinburgh. [dec. 19 , 
We think it probable that the occurrence of the acid, as a bye- 
product in the preparation of the secondary phosphine, is due to the 
digestion of the latter with strong potash solution. 
B. Solid Substance separating from the Aqueous Solution ob- 
tained by treating the contents of the tubes with Water. — This 
separated out spontaneously from the aqueous solution after it had 
been concentrated, and consisted of a white powder stained brown 
by iodine. 
On boiling with dilute spirit the crystals dissolved, and on cool- 
ing the solution deposited colourless very thin plates, which, when 
dried, had the lustre of mother-o’-pearl. 
An analysis was not made, as the melting point, reactions, and 
appearance of the salts which the substance yielded proved suffi- 
ciently that it was dibenzyl phosphinic acid. 
It may here be mentioned that this body is also produced when 
chloride of benzyl and phosphonium iodide are heated alone in sealed 
tubes, the product of action being afterwards treated with water. 
C. Viscous Substance remaining in the Alcoholic Mother Liquors 
after Dibenzyl Phosphine had crystallised out. — This was squeezed 
out through a linen filter from the crude dibenzyl phosphine, and 
was obtained in considerable quantity. Various experiments were tried 
with it, but without getting any satisfactory results. At last it was 
found that boiling water dissolved a portion, and that in concentrat- 
ing an oily liquid separated out, which partly solidified on cooling. 
By draining the crystals thus obtained on filter paper, and re- 
peated recrystallising them from hot water, a product of constant 
melting point, viz., 104° to 105°, was obtained. 
On analysis the following numbers were obtained : — 
I. II. III. 
Carbon, . .71-5 71 *3 71*7 
Hydrogen, . . 6'86 6'96 6*78 
The body had the following properties : — 
(1) When heated most of it appeared to distil unchanged, but 
at the same time an odour similar to that of the primary phosphine 
was noticed. 
(2) When its aqueous solution was mixed with caustic potash. 
It was precipitated unchanged. 
