Alcoholic Fluids^ Oils, ^c. in Lamps. 65 



whom were repeatedly discussed all these experiments on colour- 

 ed flame, &c. It was stated by him, that glass or mica introduced 

 into a blue flame, produced yellow light ; but it was immediate- 

 ly shewn, that when a glass-rod was brought to a white heat, 

 and thereby perfectly cleaned, previous to its being introduced, 

 when cold, into a blue spirit flame, no change of colour was pro- 

 duced ; and that the yellow light proceeded from some foulness 

 of the glass. Apparently clean glass and wire kept for a length 

 of time exposed in a room with a fire, have been observed to 

 change the colour of blue flame. But as soon as the glass or 

 wire is made red-hot, the yellow light disappears, and cannot be 

 made to reappear without a renewal of the combustible substance 

 on their surface ; and hence a monochromatic lamp giving a yel- 

 low light, cannot be constructed by a coil of wire in the centre 

 of a blue flame. 



Various salts, such as the muriate of barytes, the muriate of 

 soda, &c. are well known to give a yellow colour to flame ; and 

 it has been supposed, that the yellow light was produced by the 

 water of crystallization ; but in this case, it would be difficult to 

 imagine why the sulphate of alumina and potass, and other salts, 

 should produce no change on blue flame, and that the muriate of 

 lime should give it a beautiful crimson colour. The water of 

 crystallization may be accessary to the production of coloured 

 light ; but it does not seem evident that it is the primary cause. 

 By means of the blue flame of diluted alcohol, and the muriate 

 of soda, a steady flame, extricating yellow light, may easily be 

 kept up. An opportunity occurred about a year ago, of show^ 

 ing to the gentleman formerly mentioned the following simple 

 experiment. A narrow slip of paper, or of thin soft muslin, 

 well soaked in a solution of the muriate of soda, was rolled on a 

 short and rather wide glass-tube ; and the roll was retained and 

 defended by another wider tube passed over it. This, as a collar, 

 was placed on the glass-burner of a lamp for burning alcoholic 

 fluids, and when the lamp was lighted, the collar was brought 

 up so as to bring the circular edge of the paper into contact with 

 the base of the blue flame ; and in this way a steady conical 

 yellow flame was produced. A collar, consisting of several rolls 

 of a particular kind of paper was preferred for experiment, the 

 roll being easily raised between the tubes by tlie hand, after the 



APRIL— JULY 1826. E 



