the Theory of Luminous Flames. 373 



is found by the shadow test to contain solid matter ; this 

 doubtless consists of finely divided osmium. 



Kersten states that several metallic chlorides, when brought 

 in the state of solution into the flame of a Bunsen's lamp, 

 cause that flame to become luminous. Those chlorides which 

 thus produce luminosity are, according to Kersten, ferrous, 

 cuprous, palladium, and gold chlorides ; chlorides of zinc, an- 

 timony, platinum, silver, tin, mercury, as also chlorides of 

 the alkali-metals and alkaline earths, do not, according to the 

 same authority, cause the Bunsen flame to become luminous*. 



These chlorides may cause luminosity by deposition of metal, 

 or by decomposition of hydrocarbons by means of chlorine, 

 and consequent production of carbon within the flame. 



In my experiments I substituted the flame of hydrogen or 

 carbon monoxide for that of the Bunsen lamp. I found that 

 the introduction of iron, platinum, and copper chlorides caused 

 these flames to become luminous. The metallic chlorides were 

 used in the solid state, as I found that the few drops of solu- 

 tion which could be introduced into the flame on a platinum 

 wire spirted very much, and contained an extremely small 

 quantity of solid matter. The following Table presents the 

 results of the examination of a series of metallic chlorides and 

 of other salts. 



Non-luminous Flames 

 Became luminous by the intro- Did not become luminous by the 

 duction of:— cc introduction of: — 



CD 



Platinum chloride ") §■ Lead chloride, \ (blue-white"") £g 



Iron chloride | p Lead nitrate J colour) .... J g 



Chromyl dichloride )> o Alkali and alkaline-earth ^ £T 



Osmic acid | gf. salts | ►_* 



Ammonium dichromate . . . . J g Boric acid (green colour) . . J g" 



o 



Silver nitrate (blue colour). ' 



Stannous and stannic chlo- 

 rides (blue colour) 



Manganous chloride (greenish 

 colour) 



Gold chloride (greenish 

 colour) 



Cuprous and cupric chlorides 

 (blue and green colours) , . 



r w 



p 



c 



Arsenic and its salts (white-") 

 yellow colour) [ 



Antimony and its salts ( 



(whitish colour) J 



Mercuric chloride. 



Magnesium chloride. 



Silver chloride. 



If the substances which are brought into the flame be non- 

 volatile at the temperature of the flame, yellowish-white light 

 is alone emitted, the flame appears very luminous and affords 



. * In one of Davy's early papers I find an experiment described in which 

 cupric chloride was used to bring about luminosity in a flame. 



