1888-89.] Dr Haycraft on Chromatology of the Bile. 
193 
colour. The experiment may be performed in, perhaps, a more satis- 
factory manner by dipping a piece of blotting-paper in the bile, and 
laying it directly on the terminals. The brown colour changes near 
the positive terminal, first to green, then to blue, and finally to violet. 
At this stage, however, much of the pigment becomes bleached, so 
that the violet is not so distinct as either the blue or the green. 
The lower oxidation products of bilirubin can be reduced artifi- 
cially. If some bile be acidulated with impure nitric acid, so as to 
oxidise its bilirubin to biliverdin or bilicyanin, and if pieces of 
blotting-paper be then dipped in these, the vapour of ammonium 
sulphide can reduce them. The blue colour is reduced through 
green to brown, and it can then be oxidised by nitric acid. If blot- 
ting-paper is soaked in bile and reoxidised by the positive pole of 
the battery, the pigment is again reduced on reversing the poles. 
The brown can be oxidised to green and then to blue, and afterwards 
reduced to brown, passing through green. If oxidised to red, re- 
ducing reagents then change the colour to a yellow-brown, but not 
through any intermediate stages. Oxidising agents restore the 
original red colour. 
It is much easier to perform these experiments with bile than 
with pure bilirubin. Bilirubin dissolved in caustic soda is difficult 
either to oxidise or to reduce. Pure bilirubin, powdered on blotting- 
paper, moistened with normal saline solution, can be oxidised and 
reduced without difficulty by the current given by three or four 
Groves. 
On the Identity of Hofmann’s “ Dibenzyl-Phosphine ” 
with Oxide of Tribenzyl-Phosphine, and on some 
other Points connected with the Phosphorised De- 
rivations of Benzyl. By Professor Letts and R, F. 
Blake, Queen’s College, Belfast. 
(Read May 20, 1889.) 
In his well-known researches on the phosphines, Hofmann has 
shown (or believes that he has shown) that when an alkyl iodide (or 
other haloid derivative) is heated with phosphonium iodide and 
oxide of zinc, primary and secondary phosphines alone result; 
whereas, when an alcohol is heated with iodide of phosphonium, 
tertiary and quaternary phosphines are formed exclusively. Thus 
VOL. xvi. 4/7/89 N 
