Luminosity of Gases. 129 



is supplied with a spray of copper chloride, it is tinged wholly 

 green and is surrounded by a green halo. Round such a 

 flame the existence of cuprous chloride is impossible, and 

 when a piece of asbestos, soaked in hydrochloric acid, is intro- 

 duced into the halo we do not get as a matter of fact any blue 

 colour, but the ruddy margin immediately appears, and it 

 seems impossible to attribute this to anything but the forma- 

 tion of cupric chloride, which, in the presence of oxygen and 

 hydrochloric acid, remains as such and gives the feeble red 

 glow. 



The behaviour of cupric chloride in the separator admits of 

 easy explanation. In the inner cone the average temperature 

 is extremely high, and the products there generated consist 

 largely of carbon monoxide and free hydrogen. The cupric 

 chloride will therefore not only lose its chlorine but the 

 cuprous chloride, if we suppose it to be formed for a moment, 

 will be immediately attacked by the reducing gases and lose 

 the remainder of its chlorine. We have therefore metallic 

 copper, and the average temperature is not sufficient to 

 produce its characteristic spectrum. The copper and the 

 hydrochloric acid resulting from the decomposition of the 

 cupric chloride pass upwards. Some of the former is deposited 

 as a thin metallic film on the inner walls of the outer tube. 

 The rest passes to the outer cone where, at the lower average 

 temperature and in contact with atmospheric oxygen, some 

 cuprous oxide is formed and gives the green tint and oxide 

 spectrum. At the same time some cuprous chloride is formed 

 by the hydrochloric acid, and gives the faint traces of the 

 chloride spectrum. 



It is important to observe that, according to the above 

 explanation, cupric chloride is decomposed in the inner cone 

 without evincing any spectrum at all. The fact that the salt 

 is easily reduced to cuprous chloride at a comparatively low 

 temperature, and that cuprous chloride can itself be easily 

 deprived of its chlorine by heating in a current of gases of 

 the same composition as those that are passed into thQ 

 separator, would lead one to the conclusion that the salt under- 

 goes these changes before actually entering the inner cone. 

 In this case we might at first expect to see some coloration 

 below it, and, indeed, Gouy (loc. cit. p. 29) describes such an 

 appearance, stating that a line of coloration is distinctly 

 visible parallel to and within the cone. I have repeatedly 

 tried to verify this observation, but could not succeed in doing 

 so either by the eye or the spectroscope. The matter is, 

 however, of no great consequence. 



Phil. Mag. S. 5. Vol. 39. No. 236. Jan. 1895. K 



