Manchester Memoirs, Vol. lii. (1908), No. 1*^. 5 



for arsenic as in the preceding experiment, but not a 

 trace of arsenic was detected. 



{c) In the dark. 



The experiment was repeated at the ordinary tem- 

 perature for the same length of time, but no arsenic could 

 be detected in the contents of the tube. 



Action of Selenium on Stibine. 

 (a) In sunlight. 



Stibine, prepared in a similar manner to arsine as 

 above, was passed over powdered selenium contained in 

 a glass tube exposed to sunlight. The escaping gas was 

 passed over paper moistened with solution of lead 

 acetate. This very soon blackened and the stains 

 produced were not rapidly removed either by hydrogen 

 dioxide or hydrochloric acid, and after a time they 

 became orange coloured owing to separation of selenium. 

 During the experiment it was noticed that a brown film 

 slowly formed on the glass tube containing the selenium, 

 showing that in this case also a secondary reaction 

 occurred between the liberated hydrogen selenide and the 

 stibine : 



2SbH3 + 3H.^Se = SboSe, + 1 2H. 



{b) At a temperature of 100° C. 



Stibine was then passed over powdered selenium 

 contained in a U-tube immersed in boiling water and 

 -screened from light. 



As the selenium melts so readily that it might stop 

 the passage of the gas, small portions were placed in the 

 U-tube, separated by plugs of cotton wool. At the exit 

 a tube was placed containing paper moistened with 

 solution of lead acetate. Soon after the experiment 

 began, the lead paper became stained and eventually was 



