14. Interaction of phosphorus halides and arsenious 
and arsenic compounds. 
By Naagenpra Nata Sen, M.Sc. 
A Michaelis has shown that phosphorous chloride and 
arsenious oxide react in the dry state according to the equa- 
tion 5As,.0,+0PCl, = 4As+3P,0,+6AsCl, and that phos- 
phorous chloride and arsenic oxide appear not to react even at 
200°. (Zeitschr. f. Chem. (2) vii, 151, from Jenaische Zeitschr. 
vi, 240). 
But a very interesting and curious reaction takes place - 
when phosphorous halides, viz. phosphorus _ tri-chloride, 
phosphorus tri-bromide and phosphorus tri-iodide are added to 
an aqueous solution of arsenious oxide. en a few drops of 
phosphorus tri-chloride are added to an aqueous solution of 
stance takes place. This substance has been analysed and found 
to be pure elementary arsenic. During the reaction a vigorous 
evolution of heat and hydrochloric acid fumes occurs. Phos- 
the hydrolysis of phosphorus tri-chloride. Experimen 
therefore. performed with pure free phosphorous acid solution 
and an aqueous solution of arsenic tri-oxide in presence or ab- 
sence of hydrochloric acid. But no reduction to metallic 
arsenic was observed however long the mixture might be pre- 
served at temperatures varying from 0°C to the boiling point 
of the solution. With phosphorus tri-chloride also previously 
dissolved in water whether at O°C or at room temperature no 
reduction takes place even on boiling. ea 
With phosphorus tri-bromide and phosphorus tri-iodide 
the same reactions take place with certain special charac- 
teristics. The reaction is slower when phosphorus tri-bromide 
or phosphorus tri-iodide is directly added to arsenious oxide 
solution; the Jatter turns yellowish brown and the colour 
colour, but with phosphorus tri-iodide it is red brown and 
contaminated with traces of red phosphorus, probably result- 
