210 W THE THEORY OF C0.KBl7STrotf . 



phofphorus previous to its conversion into a product ? It can- 

 not combine with the new fupporter that is evolved, becaufe 

 it is a part of this theory, that light is no conflituent part of 

 fupporters, but only of combuftibles ; it fhould therefore have 

 been made evident to the fenfes, which we do not ever find 

 to be the cafe, nor is any heat evolved ; this latter effect is no 

 doubt very eafily explained, but what becomes of the light 

 yet remains to be (hewn. 

 Sulphurous and Sulphuric acid, fays Dr. Thomfon, is a fubftance which 

 fulphuric acids, from many of its properties I conclude to be a combuftible, 

 and not a product. This conclufion, however, does not ap- 

 pear to be perfectly confiftent with the definition the Doctor 

 has given of combuftion, for when fulphur is heated in the air 

 to the temperature of 302 degrees, it gives out light and heat, 

 and is converted into an acid, viz. fulphurous acid : this ac- 

 cording to the theory under consideration is a complete act of 

 combuftion, and therefore only a product of combuftion, and 

 not a combuftible body ought to be formed. Sulphurous acid, 

 according to La Grange, combines flowly with oxigen, and 

 is converted into fulphuric acid, but as no light and heat are 

 rendered vifible, ought it not in this cafe rather to be confi- 

 dered as an act of oxigenation ; for if light and heat were 

 evolved in this procefs, it fhould appear that combuftibles are 

 capable of giving out a part only of their light in fome cafes, 

 arid the whole in others, which does not appear very proba- 

 ble, for it cannot be doubted but that in fulphurous acid, the 

 oxigen and the fulphur mutually faturate each other, and that 

 fulphuric acid is only fulphurous acid combined with an addi- 

 Dceompofition tional dofe of oxigen. Though the Doctor apparently recon- 

 . of water by iron c jj es t i iC decompc.fition of water by iron or zinc with his the- 

 ory, it yet appears to be atte$d$j$ with fome difficulties which 

 are not eafily explained. — " Whenever, fays he, the whole of 

 the oxigen is abftracted from products, the combuftibility of 

 their bafe is reftored as completely as before combuftion, but 

 no fubftance is capable of abftracting the whole of the oxigen 

 from fuch products, except a combuftible, or partial combuf- 

 tible. Water, for inftance, is a product of combuftion whofe 

 bafe is hidrogen ; to reftore the combuftibility of the hidrogen, 

 we have only to mix water with iron or zinc filings, when 

 the metal is oxidated, and the hidrogen gas is evolved as com- 

 buftible as ever." Let us here attend to the phenomena 



which 



