Prof. R. Bunsen on Flame Reactions. 91 



reactions, are arranged in the following groups and subgroups 

 according to their behaviour in the reducing and oxidizing 

 flames : — 



A. Elements which are reducible to metal and are deposited 

 in films. 



1. Films scarcely soluble in cold dilute nitric acid — tellu- 

 rium, selenium, antimony, arsenic. 



2. Films slowly and difficultly soluble in cold dilute nitric 

 acid — bismuth, mercury, thallium. 



3. Films instantly soluble in cold dilute nitric acid — cad- 

 mium, zinc, indium. 



B. Elements reducible to the metallic state, giving no film. 



1. Not fusible to a metallic bead. 



a. Magnetic — iron, nickel, cobalt. 



b. Non-magnetic — palladium, platinum, rhodium, iri- 



dium. 



2. Fusible to metallic beads — copper, tin, silver, gold. 



G. Elements most easily separated and recognized as com- 

 pounds — tungsten, titanium, tantalum and niobium, silicon, 

 chromium, vanadium, manganese, uranium, sulphur, phosphorus. 



T now proceed to consider the special behaviour of the bodies 

 named in the foregoing groups. 



1. Behaviour of the Tellurium Compounds. 



(a) Flame-coloration. — In the upper reducing flame pale blue, 

 whilst the upper oxidizing flame appears green. 



(b) Volatilization unaccompanied by any smell. 



{c) Reduction film black, thinnest part blackish brown, dead or 

 bright; heated with concentrated sulphuric acid gives splendid 

 carmine-red colour. 



(d) Oxide-film white, invisible or nearly so ; stannous chloride 

 colours it black from reduced tellurium ; silver-nitrate, after 

 blowing with ammoniacal air, yellowish white. 



(e) Iodide-film blackish brown, thinnest part brown ; disap- 

 pears momentarily on breathing upon it, but not when slightly 

 warmed ; reappears on exposure to hydrochloric acid ; blackened 

 by stannous chloride. 



(f ) Sulphide-film blackish brown to black ; does not disap- 

 pear by breathing ; soluble in sulphuretted air ; reappears on 

 warming or by dry blowing. 



(g) On the charcoal splinter with soda yields a sodium-telluride, 

 which, when moistened, leaves a black mark on a silver coin ; 

 and if the sample contains much tellurium, gives off a smell of 

 telluretted hydrogen when moistened with hydrochloric acid. 



