4*04 British Association for the Advancement of Science. 



by long standing it is decomposed by it. Chlorine bleaches it slowly ; 

 caustic alkalies redissolve it. It is scarcely bleached at all by the 

 sun's rays, nor does it when properly washed and dried show any 

 tendency to deliquesce ; it therefore is an excellent colour for pa- 

 per-staining and other such purposes, as few common agents will in- 

 jure it, and it can be readily removed from surfaces by an alkali*. 



The proportions of useful products above given can only be con- 

 sidered as approximations, having been deduced from experiments 

 on a small scale ; they would probably be much increased, and the 

 relative expense of preparing the material reduced, if the process 

 were carried on with greater quantities. 



On some singular Phcenomena of Flame from Coal- Gas. By R. 



Mallet. 



If an Argand gas-burner be lighted, and a conical tube of a cer- 

 tain diameter be inserted concentrically within it, with its extremity 

 entering a certain distance, within the burner, and, while the gas is in- 

 flamed, a current of air be propelled through the conical tube in the 

 same direction with the streams of gas, under certain conditions, the 

 whole of the gas-flame will retract or be drawn back between the 

 internal surface of the burner and the external surface of the conical 

 tube, and nothing whatever will pass forward but a stream of 

 strongly heated carbonic acid and aqueous vapour. This very sin- 

 gular phaenomenon of the passage in opposite directions of two cur- 

 rents in such close contact does not appear to be affected by the size 

 of the burner, provided a certain proportion be preserved between 

 it and the conical air-tube. The experiments were made with two 

 burners chiefly, one of which was three quarters of an inch internal 

 diameter and one and a half inch deep, measured along its axis, 

 and the other seven sixteenths of an inch internal diameter, and one 

 and three eighths inch deep. 



"With these it was found that the retraction of the flame was pro- 

 duced most perfectly in the. case of the large burner by a tube of 

 five sixteenths of an inch diameter, but yet took place to a certain 

 extent until the diameter of the tube was reduced to one eighth of 

 an inch, and in the case of the smaller burner it was most perfectly 

 produced by an air-tube of three sixteenths of an inch diameter ; 

 yet taking place in a slight degree with one of only one twentieth of 

 an inch diameter. 



If the conical air-tube be not inserted into the burner, but merely 

 held close to its base or lower aperture, no retraction takes place, 

 the flame is merely curtailed, and the combustion rendered more 

 perfect ; and the same result takes place when a tube equal in dia- 

 meter to the internal part of the burner is used, in which case it is 

 obvious none of the flame could retract. 



To the perfect production of the foregoing effects it is necessary 

 that the apertures for the gas in the burners be of a much smaller 



* [See a paper by the late Dr. Macculloch, in Trans. Geol. Soc., first series, 

 vol. ii. ; or Phil. Mag., first series, vol. xliv. pp. 215, 271.— Edit.] 



