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VI. On the Effect of Chlorine in Colourinrj the Flame of Burning 

 Bodies. ' By D. Forbes, F.G.S., F.C.S., A.I.C.E.^ 



A CONSIDERABLE time back, whilst examining some saline 

 ^^ minerals for boracic acid, and employing tlie usual test as 

 to tbe power of colouring flame green, when treated with sul- 

 phuric acid and alcohol, it was found that a green flame presented 

 itself, very similar to that which would be expected in case boracic 

 acid were present in the minerals. On the most careful exami- 

 nation, however, no traces of boracic acid could be detected, and 

 it was evident that the coloration of the flame must have pro- 

 ceeded from some other source. 



As chlorine was present in considerable amount in the mine- 

 rals in question, it became interesting to see whether its presence 

 might have produced the green colour; and the experiments 

 made on the subject fully confirmed this view. A number of 

 further experiments on the power possessed by chlorine to colour 

 flame, led to the following conclusions, which are stated briefly, 

 as the results themselves sufficiently explain the modus operandi. 



Chlorides treated with concentrated sulphuric acid and a very 

 small amount of alcohol, produced green flames similar to those 

 eliminated from borates under like treatment. Quantitatively, 

 however, the flames were of less intensity ; that is, the same weight 

 of a borate would produce considerably darker green flames than 

 when a chloride was used. 



When chlorides were moistened with sulphuric acid and heated 

 in the blowpipe flame, a faint green coloration was observed, 

 which generally confined itself to the inner flame. 



When hydrochloric acid is dropped cautiously on the flame of, 

 burning alcohol, a greenish tinge is observable. 



A jet of chlorine or of hydrochloric acid gas directed upon the 

 flame of a spirit-lamp or of coal-gas, produces a jet of green 

 flame ; this was also found to be the case when (by means of a 

 convenient burner) chlorine gas was passed into the centre of a 

 flame of burning coal-gas, or of vapour of alcohol. 



When burning alcohol was injected into a globe filled with 

 chlorine gas, the alcohol vapour continued burning at the mouth 

 of the globe with a very flickering but often brilliant green flame. 



From the above experiments, it will be seen that chlorine has 

 in itself a decided colouring action on the flame of burning bodies, 

 which may consequently in some cases lead to its being con- 

 founded with boron, as the green colour im])arted to flame has 

 hitherto been regarded as a most characteristic test of the latter 

 element. When, as often happens, chlorine and boron occur 

 together, this test consequently becomes nearly valueless. 

 * Communicated by the Author. 



Phil. May, S. 4. Vol. 1 1 . No. G9. Jan. 185G. F 



