10.2 Prof. R. Bunsen on Flame Reactions. 



lain plate, is mixed on the hand with soda, obtained in a pasty 

 state by melting a crystal. The mixture is then transferred on 

 to a spiral of fine platinum wire and fused in the flame ; the 

 liquid fused mass is then knocked off the wire and allowed to fall 

 upon the plate, when it is digested with two or three drops of 

 water, and the clear supernatant liquid absorbed by three or four 

 strips of filter-paper a few millimetres in breadth. 



(a) One of these strips, on moistening with hydrochloric acid, 

 does not change colour, but on addition of a drop of potassium- 

 ferrocyanide it is coloured a reddish brown. 



(/3) If one of the strips be gradually moistened with a few 

 milligrammes of stannous chloride, it is coloured blue either at 

 once or on gently heating ; if the tint be yellow or light brown, 

 a few drops of soda solution must be added by a capillary tube 

 until the blue colour appears. 



(7) A drop of ammonium-sulphide added to the third strip 

 produces a brown coloration ; and on addition of hydrochloric 

 acid a brown precipitate is formed, the paper, at the circumfe- 

 rence of the drop, often being coloured blue. 



(8) The yellow phosphate precipitate produced by the nitric 

 acid solution of ammonium-molybdate can also be readily ob- 

 tained. 



(c) The. borax bead is not very characteristic ; in the oxidizing 

 flame it is colourless, and in presence of much molybdenum it 

 becomes opake; in the reducing flame it is dark from reduced 

 molybdenum. 



25. Tungsten Compounds. — The reduction of tungsten can 

 likewise be made on the charcoal splinter with soda, but this 

 method is not available for the detection of the metal. The 

 tungsten compounds are therefore best examined in the mode 

 described under molybdenum, by absorbing the liquid obtained 

 by fusion with soda on some strips of filter- paper. 



(a) One strip is moistened with hydrochloric acid ; it remains 

 white, but on heating turns yellow ; moistened with ferrocyanide 

 it is unaltered. 



(/S) A second strip, touched with stannous chloride, is coloured 

 blue in the cold or on heating. 



(7) A drop of ammonium- sulphide causes no precipitate either 

 by itself or after addition of hydrochloric acid ; the paper becomes, 

 however, blue- or greenish-coloured, especially on warming. 



26. Titanium Compounds give a colourless bead with micro- 

 cosmic salt in the oxidizing flame, which turns of a pale ame- 

 thystine colour in the reducing flame. On addition of ferrous 

 sulphate the bead assumes in the reducing flame the peculiar red 

 colour of venous blood, whilst in the oxidizing flame the light- 

 brown colour of ferric oxide can be obtained at pleasure. The 



