42 ON THE DOCTRTNE OF PHLOGTSTOW, 



IX. 



Ohfervatiowt in Anfiver to Dr. Priestley's Memoir in De- 

 fence of the Doctrine of Phlogijlon *. In a Letter from Mr. 

 William Cruickshank. 



To Mr. NICHOLSON. 



SIR, Woolxiich, March 22, 1802. 



1 N your Journal published the \jl of this month, I find a letter 

 from Dr. Prieftley, in which he (till defends the old doclrine of 

 phlogifton, but with very little fuccefs ; for having additional 

 difficulties to ftruggle with, he has been under the neceffity of 

 adopting new, and fometimes contradictory opinions, in his 

 Obfcrvations of explanations and defence ; For example, it is now his opinion 

 that metallic tliat al * metallic calces contain water and little or nothing elfe; 

 calces contain and that charcoal, uniting with water, forms both fixed and in- 

 little addition flammable air ; for as this fubftance contains the elements of 

 except water. . 



both kinds, nothing but water is wanted to enable them to take 



the form of air. It is almoft impoffible to argue againft fuch 

 ftrange fuppofitious and loofe reafonings asthefe. However, 

 let us fuppofe water to be the only fubftance contained in ox- 

 ides ; if fo, heat alone ought to revive at leaft fome of them, 

 But when re and in this cafe nothing but water mould be feparated. Now 

 heat they Tfford ** iat neat a ^ one revives feveral, particularly thofe of mercury 

 pure oxigen, and the perfect metals, is a fact fufficiently afcertained ; but, 

 toThe^rlofsof H1 ^ ea ^ of water, we obtain the pureft oxigen gas, the quantity 

 weight, and no of which added to the revived metal, amounts, as nearly as 

 w * ter * poffible, to the weight of the original oxide ; even from the ore 



of manganefe, fo difficult to reduce, a prodigious quantity of 

 the pureft oxigen gas may be procured by a moderate heat ; 

 and when the oxide has been previoufly reduced to powder 

 and well dried, by a heat nearly red, no water whatever can be 

 perceived : in this cafe, too, the quantity of the oxigen gas dif- 

 engaged, will be found to correfpond very nearly with the lofs 

 of weight in the oxide. 

 If calces contain How is it poflible, then, that thefe phenomena can be ex- 

 water only, then pi amec i on tnc fuppofition, "That all the calces contain little 



charcoal muft r rr 



produce the fame . ,>,.,/• , , t ,„, 



' * Philof. Journal I. 131. 



''or 



