92 Prof. R. Bunsen on Flame Reactions. 



2. Behaviour of the Selenium Compounds. 



(a) Flame-coloration — the bright blue of the corn-flower. 



(b) Volatilizes and burns, giving off the peculiar putrid smell 

 of selenium. 



(c) Reduction film brick-red to cherry-red, sometimes dead, 

 sometimes bright ; heated with strong sulphuric acid, gives an 

 olive-green solution. 



(d) Oxide-film white ; on addition of stannous chloride, brick- 

 red from liberated selenium ; the red colour becomes darker on 

 addition of caustic soda; silver nitrate gives a white not easily 

 visible coloration, which disappears in a current of ammoniacal 

 air. 



(e) Iodide-film brown, contains some reduced selenium, and 

 hence cannot be completely removed either by blowing with am- 

 moniacal air or by breathing. 



(/) Sulphide-film yellow to orange-red, insoluble in water, 

 soluble in ammonium-sulphide. As the sulphide is prepared 

 from the iodide, it also contains free selenium, and does not give 

 very clear reactions. 



(g) Reduction with soda on the charcoal splinter gives sodium- 

 selenide, producing a black mark on a silver coin when moist- 

 ened, and giving rise, if the quantity be not too small, when 

 touched with hydrochloric acid, to red selenium and a smell of 

 seleniuretted hydrogen. 



3. Behaviour of the Antimony Compounds. 



(a) Flame-coloration, by treatment in the upper reducing flame, 

 pale green, unaccompanied by any smell. 



(b) Reduction film black, sometimes dead, sometimes bright. 



(c) Oxide-film white ; moistened with perfectly neutral silver- 

 nitrate solution and then blown on by ammoniacal air, it gives 

 a black spot which does not disappear in ammonia. If the 

 film be first placed over bromine-vapour the reaction cannot 

 be obtained, owing to the oxidation of antimonious to anti- 

 monic acid. It is unaltered by stannous chloride, either with or 

 without caustic soda. 



(d) Iodide-film orange-red, disappearing by breathing, and re- 

 appearing by blowing or warming : blown on with ammoniacal 

 air it disappears, but does not return; generally it gives the 

 same reactions as the oxide. 



(e) Sulphide-film orange-red; the film is difficult to blow 

 away with sulphide of ammonium ; returns on blowing with air ; 

 insoluble in water. 



(/) With soda on charcoal splinter gives no black stain on silver, 

 but yields a white brittle metallic bead. 



