]70 CHtMlCAL THJecrvY. 



Dissertation on in a pure and detatched state, and capable 0f entering cer- 

 c:"ects of heat ^^^^ substances, without affecting either the organs of vision ' 

 litriit, and com- or of toUch, as is observed when it enters a product of com- 

 bustion. , 



bustion. 



The effect of galvanism varies with different inflammable 

 substances according to the intensity of heat which is ne- 

 cessary for their combustion ; phosphorus, hydrogen, car- 

 bon, and sulphur, inflame at low temperatures, and therefore- 

 are immediately set on fire ; but the metnls which I consider 

 as inflammable substances, are more difficultly ignited, and 

 are capable of retaining s considerable quantity of the elec- 

 tric fluid witho it undergoing change; but even these are in- 

 flamed by a po\>erful instrument. 



In treating of combinations of oxigen with other sub- 

 stances much ambiguity has arisen among chemists; for no 

 one can suppose that the oxigen which is contained in the 

 products of CO!), bustion is the same as oxigen gas, which is 

 a supporter of cosiibustion. An ingenious philosoj her of 

 Italy * observing this circumstance, has endeavoured to re- 

 medy it by suj)posing oxigeu able to combine with sub- 

 stanc s retaining its heat, as in nitric and oxi-muriatic acids; 

 and in its simple state as in the sulphuric and carbonic acids, 

 but as he supposed that I>eat and a base were the component 

 parts of oxigen gas, he called it thermoxigeuj as retaining its 

 heat ; but, as I have differed fi'om him in supposing it a 

 compound of light and a base, I may call it photoxigen. 



It is a question which, 1 must coiifess, I am unable to re- 

 solve, whether the matter of light can exist in substances 

 without the presence of oxigen ? But thus far may be said, 

 that oxigen and light are capable of combining with other 

 substances, and thereby may be in a dense form, as is seen 

 in the acid supporters, and certain metallic supporters. Ni- 

 tric acid therefore we may state as a combination of oxigen, 

 light, and another substance called azote, which has hitherto 

 been called an element ; but whether it is the base of any 

 substance, or can be united with the matters of heat and 

 ligl;t, I am unable to determine. It has long leen known 

 that the component parts of nitric acid were the same as that 

 of atmospheric air, but that the proportions of different sub- 



* IjrugnateUi. 



stances 



