1826.] Mr. RuchtVs Experiments on Radiant Heat, 17 



a mercurial thermometer with the bulb blackened ; but have not 

 succeeded in obtaining any difference between the effect when 

 the screen was opaque and when transparent. 



These last experiments are detailed in the latter part of a 

 paper which was read before the Royal Society on Thursday, 

 June 1, the primary object of which was to examme a particular 

 instance, in which M. De la Roche had concluded that simple 

 heat permeates glass by direct radiation. If my experiments 

 are to be relied on, that conclusion is rendered unnecessary, the 

 facts having been shown to admit an explanation on the common 

 principle of a secondary radiation. The experiments in the 

 present paper were not made till after that communication had 

 been sent to the Royal Society, which was on the 9th of March 

 last, or they should have formed a part of it. 



J';:r < 



Article III. 



On the Production of Acetic Acid, in some original Experiments 

 with Metallic and Non-metallic Substances over Ether^ Alcohol, 

 S^c, By H. B. Miller, Esq. 



(To the Editors of the Annals of Philosophy/.) 



GENTLEMEN, Bristol, May U,IS26. 



Having observed in your number for April, a notice of some 

 experiments by Mr. Murray, in which it had been discovered 

 that gum arabic, heated to redness on a slip of platinum foil, 

 became incandescent when held over ether in a state of sponta- 

 neous evaporation (similar to the well-known experiment of 

 Sir H. Davy with a coil of platinum wire), I immediately insti- 

 tuted a series of experiments, of which the following is a detail, 

 to ascertain whether the carbonaceous residue after the decom- 

 position of the gum by heat alone produced this effect ; and also 

 to discover if the vapour of acetic acid is produced by the com- 

 bination of the gases, as is the case when platinum continues in 

 a state of ignition over alcohol, ether, &,c. In the following 

 experiments, ether, alcohol, essential oils, and mixtures of the 

 oxygen and hydrogen gases, carburetted hydrogen and air, 

 olefiant gas and air, produced similar effects, viz, the incandes- 

 cence of the substance experimented on. 



Exp. 1.— Charcoal from wood effected the combination of the 

 gases very rapidly ; it continued incandescent for a considerable 

 time over ether. 



Exp. 2. — Charcoal from the decomposition of bones. 



Erjj, 3. gum arabic. 



Exp. 4. tragacanth. 



Exp. 5. myrrh. 



These substances all yielded results similar to common charcoal. 



New Series, vol. xii. c 



