62 Mr H. H. Blackadder on the Combustion of 



it is burned with a wick, there is a constant buzzing noise, with 

 an appearance as if this noise was produced by an infinity of mi- 

 nute explosions at that part of the flame where the narrow bhie 

 line appears. It is particularly to be observed, however, that 

 this part of the flame remains unchanged, and that it is the ex- 

 terior brush flame that is changed from a pale misty-blue to a 

 mat-yellow colour. The blue flame of alcohoHc fluids may be 

 made to swell out or expand, by touching the fluid as it issues 

 from the burner, with a hot wire, and without, in any degrecj 

 altering the colour of the flame ; and, in this case, there is simply 

 an increase of the distillation. But, with the same wire, or with 

 a rod of glass, the mouth of the burner may be so touched as to 

 produce a discharge of small particles of the fluid, similar to that 

 which takes place on other occasions, when a very hot piece of 

 metal is introduced into a vessel containing water. These mi- 

 nute particles are impelled against the inner surface of the flame, 

 seem to explode, and then produce the dull-yellow colour of the 

 exterior brush flame. When a wick of cotton, or of sponge, is 

 used, it acts the part of the hot wire ; and the rougher its sur- 

 face, and the nearer it approaches to the inner surface of the 

 flame, without being carbonized, the more copious is the dis- 

 charge of the particles, and consequently of the yellow light. 

 This may be farther illustrated as follows : — Let a small ball of 

 cotton thread be attached to the end of a glass tube, and moisten 

 the ball with alcohol. When the latter is made to burn, yellow 

 light is extricated ; but if the ball be now made to turn rapidly 

 on its own centre, the quantity of yellow hght will be increased 

 an hundred-fold. In this case, two causes operate ; the flame is 

 brought closer to the ball, producing a greater discharge of mi- 

 nute particles ; and, at the same time, the alcohol is expelled by 

 the rotatory motion in a thick shower into the flame. 



Steam issuing forcibly from a small orifice will answer the pur- 

 pose of a blowpipe ; and, even when it is condensed into a white 

 vapour, it has no eflect in changing the blue colour of a spirit- 

 flame. But if a small vessel of water be placed under the burn- 

 er, and a hot rod of metal be introduced, so as to discharge par- 

 ticles of the water on the exterior surface of the flame, yellow 

 light is extricated. Some of the coloured light is, in this case, ap- 

 parently produced by small solid particles from the surface of the 



