ON THE THEORY OF COMBUSTION. 209 



other part of this theory, viz. that the light emitted during proceeds from 



combuftion invariably proceeds from the burning body, an d the burning 



that confequently it forms no part of the fupporter. It of 



courfe then follows from this theory, that light is no eflential 



part in the compofition of oxigen gas. Let us however fee 



whether this be the cafe. Many fafts it will be found concur 



to prove that the contrary is the truth. If nitric acid be ex- 



pofed to the light, after fome time we find that it changes 



colour, it becomes yellow, green, and then red, and oxigen 



gas is difengaged, the nitric at the fame time being converted 



into nitrous acid. Now it is evident, that as this decompo- for the light 



fition is of a chemical nature, the light that occafions it, ei- wh j ch decom- 

 i , • . , , n • . lL pofes nitric or 



ther combines with the oxigen to form oxigen gas, or with ox# mim ac ; d i 3 



the acid to form nitrous acid : as we find no diffimilarity be- concluded to 



tween the nitrous acid procured by this means, or that by any w j t hthe difen- 



other, we are neceflitated to conclude that the light has com- gaged oxigen* 



bined with the Oxigen, and that the latter by the fame means 



is converted into, oxigen gas. Again, it is well known, if 



oxigenated muriatic acid be expofed to the rays of the fun in 



a tranfparent bottle, there is difengaged from it oxigen gas * 



in proportion as the gas is feparated the acid lofes its colour 



and odour, and returns to the ftate of fimple muriatic acid. — 



Here it is evident, that the oxigen has paned from a concrete 



into a gafeous ftate from the combination of light, and we muft 



therefore conclude that light is a component part of oxigen 



gas. 



Ifphofphorus be inferted in nitric acid, the latter is de- when phofpho- 



compofed, and a product of combuftion, namely phofphoric rus lsac,dlfiedm 



• , . ,. II- i-i r • i 1 i-i nitrous aciJ, 



acid is formed, during which procels neither heat nor light wria t becomes of 

 are given out. This procefs Dr. Thomfon confiders as an the light of the 

 act of oxigenation, and not of combuftion, becaufe, fays he, 

 though a product of combuftion is formed, a new fupporter, 

 namely nitrous gas is evolved, and the formation of a combuf- 

 tible, or new fupporter, conftitutes one of the characleriftic 

 differences between the two procehes of combuftion and oxi- 

 genation. Now it is faid, that in all cafes of oxigenation a 

 double decompofition takes place, the oxigen of the product 

 combines with the bale of the combuftible, while the light of 

 the combuftible combines with the bafe of the product. The 

 queftion then naturally prefents itfelf,—- what during this procefs 

 becomes of the light which made a component part of the 

 Vol II. —July, 1802. P phofphorus 



