252 ESSAY XXIII. 



alkali ; and what wonder that this elastic acid should be 

 expelled by a stronger ? Experiment 34 is very easy to be 

 explained ; (for, if the author's assertions were admitted, 

 calx of iron w T ould have a stronger attraction for phlogiston 

 than nitrous acid). Alkalies as well as nitre, when they are 

 mixed with metals or metallic calxes, in order to prevent 

 their fusion, lose their acids on a long-continued calcination, 

 and immediately afterwards the matter of heat unites with 

 the alkalies, which is the only cause of their causticity. 



Lead is a metal which contains very little phlogiston ; 

 for I have observed scarce any sensible mark of liver of 

 sulphur upon stratifying it with vitriolated tartar in a close 

 crucible. Should vegetable alkali have reduced any calx 

 of lead, this might have arisen from the glue that the ley 

 carried along with it on being filtered through bibulous 

 paper, or perhaps from some impurity adhering to the 

 alkali or minium. Why is not a solution of lead reduced 

 by alkali in the humid way ? Experiments 42 and 43 

 have turned out very differently, when made by all other 

 chemists, even by the late Mr. Meyer himself, as well as by 

 me ; for caustic fixed alkali always precipitates a solution 

 of calcareous earth in a caustic state. The author here 

 did not pay attention enough. Experiments 44, 45, and 

 46 are also insignificant. According to the 47th, ashes 

 adhering to red hot coals should have lost their phlogiston. 

 But if so, why do they effervesce with acids ? For, accord- 

 ing to the hypothesis, the earths effervesce because they 

 contain phlogiston. The author mentions some phenomena 

 (pp. 137 and 145), which in his opinion cannot be ex- 

 plained at all ; as for instance that alkali does not totally 

 precipitate vitriol; that vitriolated tartar does not entirely 

 precipitate the solution of quicksilver ; as also that the 

 mother ley of common salt cannot be completely precipitated 



