234 Mr Blackadder on the Constitution of Flame. 



contact. But, without the assistance of heat, water, and many 

 iQther fluids, may be made to impinge on a spirit-flame, so as to 

 cause the extrication of yellow light. For this purpose, it is on- 

 ly necessary to impel the fluid in such a way, that, in escaping 

 from the vessel in which it is contained, it shall produce a whiz- 

 zing noise, similar to that caused by the escape of soda water 

 and carbonic acid gas, through the pores of a cork ; or to that 

 produced when a hot body is dropt into water. On such occasions 

 particles are expelled of such a size as renders their explosion 

 inevitable on coming into contact with the flame ; the larger par- 

 ticles passing through without suffering more than a slight dimi- 

 nution of their bulk. Thus, let a small quantity of water be in- 

 troduced into the hollow bulb of a glass blowpipe, and on bring- 

 ing the water to a level with the distant part of the tube, let air 

 be forced through the instrument, so as to expel water from its 

 point, with a whizzing noise. Thus expelled, particles of water, 

 alcohol, sulphuric acid, and many other fluids, cause a blue flame 

 to give out yellow light. A similar discharge of fluids may be 

 produced in various other ways, and always with the same eff*ect ; 

 such as tallow mixed with water, &c. When muriate of soda is 

 placed in a flame it decrepitates, and the yellow light is brilhant, 

 in proportion to the violence of the decrepitation. The muriate 

 of baryta also decrepitates, though in an inferior degree. When 

 held near the apex of a spirit-flame, it gives out white fumes, and 

 these fumes give a yellow colour to flame. The presence of a li- 

 quid, such as water, is necessary to the formation of the fumes, 

 which seem to be simply particles of the salt, in a state of minute 

 division. It would be desirable to ascertain the effect of these 

 salts on the flame of a combustible, into the composition of which 

 hydrogen does not enter, and whose conjbustion is not supported 

 by oxygen. 



When a perfectly clean rod of glass is broken in a spirit-flame, 

 yellow light is given out ; and the same effect is produced by 

 grinding together the ends of two rods in tJie immediate vicinity 

 of the flame. Two pieces of pumice stone, that have been pre- 

 viously brought to a white heat, also cause the extrication of yel- 

 low light, when struck or ground close to a spirit-flame. Many 

 other incombustible bodies produce a similar effect ; and in such 

 cases the origin of the coloured light is very obvious. 



The gaseous oxide of carbon, during its combustion, gives out 



