170 ANNUAL OP SCIENTIFIC DISCOVERY. 



I 



means obtained, either by varying the proportion of chlorine or 

 chloride, or by varying the temperature, and the results will be the 

 same. If, for example, there is placed in pure alcohol a salt of 

 copper, to which. hydro-chloric acid is gradually added, there will be 

 produced at first a yellow flame, and all the other colors as far as 

 violet will be successively obtained. If, instead of a salt of copper, 

 there be taken some neutral per-chloride of copper, there will be 

 produced at first a yellow flame, and afterwards a green ; but there 

 will be no blue flame, except by adding hydro-chloric acid, and by 

 increasing the quantity of the above acid the violet will be attained ; 

 at last, a red flame will be produced by the largest quantity that can 

 be added without extinguishing the alcohol. Now, if I take some 

 neutral deutochloride of copper, (dry) and expose it on a sheet of 

 platinum to the flame of a spirit lamp, the alcohol quite pure, I 

 shall produce successively colored flames from the yellow to the red, 

 which latter is produced by the strongest heat that I can obtain. But, 

 having thought that with a higher temperature I could perhaps obtain 

 an orange colored flame, I made use of a Gaudin lamp with a current 

 of oxygen, and by that means obtained on a sheet of platinum, not 

 only a red flame, but a very fine orange colored flame, from the high 

 temperature that I was able to obtain a result that I had foreseen. 

 (A strong eolipile lamp may be used for this experiment.) 



If I take the same deutochloride of copper and throw it into a very 

 fierce fire, such as one composed of pit coal and wood, there will be 

 produced, almost simultaneously, flames of all the colors of the spec- 

 trum, according to the strength of the fire : and if only indigo, violet, 

 red, and orange colored flames are required to be produced, we have 

 only to add to the per-chloride of copper some hydro-chloric acid, or 

 some chloride of magnesium, in a rather large quantity. In this case 

 there will be produced jets of red flame in certain parts of the fire, 

 which will be as bright as those produced by strontium ; "but in this 

 last case, there will be scarcely any green flames, and still less yellow. 

 These two latter will be only produced towards the end of combustion, 

 or in the less heated parts of the fire ; and if there is a sufficiently 

 powerful heat, there will be produced an orange colored flame. It is 

 evident that to obtain in a fire flames of all the colors of the spectrum, 

 it is necessary to take a chloride of copper which contains only the 

 quantity of chlorine suitable for producing only a green flame by 

 burning some alcohol, and I will observe that this ray becomes the 

 middle of the solar spectrum, and that it is the same in producing all 

 the colors by light ; for it will be recollected that I have said that 

 there should be taken in this case the quantity of chlorine or chloride 

 that preferably produced the yellow and green rays. Then all the 

 colors will be produced, according to the luminous strength of each 

 ray, as the variation of heat produces flames of different colors. The 

 intensity of the heat may be (as has been seen,) recruited by a greater 

 or smaller quantity of chlorine ; and with the same quantity of chlo- 

 rine, the heat may produce the yellow flame, being the minimum, and 

 the orange, the maximum. In like manner it is observable that the 



