44 On the Combustion of Tallow, Fixed Oils, Sfc. [July, 



Article XI. 



On the slow Combustion of Tallow, Fixed Oils, and Wax. 

 By Mr. C. J. B. Williams. 



(To the Editor of the Annals of Philosophy.) 



SIR, Edinburgh, May 1, 1823. 



Permit me to draw the attention of your chemical readers to 

 a" phenomenon (hitherto, I believe, unnoticed), illustrating ihe 

 slow combustion of the inflammable gas or vapour, produced by 

 the decomposition of oleaginous matter by heat. It may be 

 manifested in the following manner : Extinguish the flame of a 

 candle or lamp by blowing on it, having previously supplied the 

 wick freely with tallow to increase the size of the flame, and to 

 prevent any portion of the wick from remaining in a state of 

 open combustion. If this experiment be made in a room 

 secluded from every other source of light, a distinct phospho- 

 rescence on the surface of the wick will be perceived during 

 several seconds, brighter in proportion to the size of the flame 

 before being extinguished ; hence it is most obvious with a long 

 wick, provided no spark be left on it. 



This combustion, which I consider analogous to that of the 

 vapour of ether, by the aid of a platinum wire, is likewise 

 attended with the production of a pungent acid vapour. Of the 

 nature of this, I have had neither time nor opportunity to ascer- 

 tain any thing. It is probably, as in the case just alluded to, 

 merely a modification of the acetic acid ; but since the odour 

 differs considerably from that of the lampic acid, it might be of 

 sufficient importance to merit an investigation. 



I have ascertained that a similar phenomenon occurs when 

 fixed oils or wax are projected in small quantities on a plate of 

 metal heated considerably below redness ; and from some expe- 

 riments I am inclined to believe that this modification of com- 

 bustion takes place in most cases where these substances are 

 heated to ebullition in free contact with the air. 



I have submitted the result of my observations on this 

 subject in this imperfect state ; as a long time might elapse 

 before I could be enabled to extend them further, and in the 

 expectation of seeing them prosecuted in abler hands. 

 I am, Sir, with respect, yours, &c. 



Charles J. B. Williams. 



