Prof. R. Bunsen on Flame Reactions. 97 



13. Behaviour of the Nickel Compounds. 



(a) Reduction on charcoal splinter. — On pulverizing the char- 

 coal the metal obtained as white, lustrous, ductile particles, form- 

 ing a brush on the magnetized blade. The metal dissolved in 

 nitric acid on paper gives a green solution, which on moistening 

 with soda, exposure to bromine-vapour, and subsequent addition 

 of soda, gives a blackish-brown spot of nickel-sesquioxide. The 

 ash of the paper, from which the excess of soda has been washed 

 out, can be used for the borax-bead test. 



(b) Borax bead. — Oxidizing flame greyish brown or dirty violet. 

 Upper reducing flame grey from reduced nickel, which often col- 

 lects to a spongy mass of metal, rendering the bead colourless. 



14. Behaviour of the Cobalt Compounds. 



(a) Reduction on charcoal splinter. — By pulverizing the char- 

 coal, as with nickel, white ductile lustrous metallic particles are 

 obtained which form a brush on the magnetic blade. The metal, 

 rubbed off on to paper, gives a red solution when moistened with 

 nitric acid ; this yields a green colour on addition of hydrochloric 

 acid and drying, which disappears again on moistening. The paper 

 moistened with soda, brought into bromine-vapour and again 

 moistened with soda, yields a blackish-brown spot of cobalt-ses- 

 quioxide. This reaction is plainly seen with a few tenths of a 

 milligramme of metal. The paper can also be used, after wash- 

 ing out the soda and burning, for the coloration of the borax bead. 



(b) Borax bead. — In the oxidizing flame a bright-blue bead, 

 unaltered in the lower' reducing flame. The bead, when held for 

 some time in the most powerful upper reducing flame, becomes 

 colourless, owing to separation of metallic cobalt : this separation 

 takes place more rapidly in presence of the platinum-ammonium- 

 chloride, when an alloy of nickel and platinum is formed. 



1 5 . Palladium Compounds. 



(a) In the oxidizing flame these compounds, heated on a fine 

 platinum wire with soda, yield a grey mass resembling spongy 

 platinum ; this yields silver-white lustrous particles when rubbed 

 up in the agate mortar. These particles, washed and dried on 

 a piece of curved glass, yield a red solution with nitric acid. 

 A drop of mercuric cyanide added to this solution forms, when 

 blown upon by ammoniacal air, a white precipitate soluble in excess 

 of ammonia. After evaporation, and on boiling with aqua regia, 

 the liquid, when evaporated to a drop, deposits a dirty-orange- 

 yellow crystalline precipitateof the ammonium-palladium-chloride. 



(b) The solution of palladium is coloured blue, green, and 

 brown by stannous chloride, according to the quantity of the re- 

 agent added. 



Phil. Mag. S. 4. Vol. 32. No. 214. August 1866. H 



