250 ESSAY XXIII. 



a constituent part of the atmosphere ; and the more exactly 

 the phlogiston combined with it is separated from it, the 

 more pure air must make its appearance. Fixed air is also 

 present in putrefying water. That the earth in lime-water 

 is restored to its crude state by phlogiston, the author can 

 neither persuade me nor any intelligent chemist. Had the 

 author examined a little less carelessly the precipitate which 

 appears on pouring lime-water into human urine, he never 

 would have pronounced it to be calcareous earth, as in 

 Experiment 19. I can assure him that this precipitate 

 does not effervesce with any acid, but is animal earth, 

 precipitated by the phosphoric acid in urine. The same 

 may be said of the 20th experiment, which the author made 

 very unnecessarily. No exact chemical experiments should 

 be made with the volatile alkali from putrid bodies. Other 

 chemists, as well as myself, have obtained by sublimation 

 good sal ammoniac from volatile alkali separated from sal 

 ammoniac by lime, and afterwards saturated with muriatic 

 acid. Neither is the fixed nor volatile alkali in neutral 

 salts caustic ; neither is the lime contained in fixed ammoniac, 

 as it is called. These substances are caustic only in con- 

 sequence of being combined with a considerable portion of 

 the matter of heat, which separates as soon as an acid is 

 poured on them, the acid having a stronger attraction for 

 the bodies than heat. I need not touch upon the 25th 

 experiment. When the lime does not slake, it can only 

 make the ley a little caustic ; for, in the last case, or when 

 the ley is to be thoroughly caustic, it must touch the corrosive 

 sublimate in all possible points. As the matter of heat 

 consists of phlogiston and pure air, while metallic calxes, 

 prepared by heat, contain much heat, which must be heavier 

 than phlogiston alone, what wonder that a metallic calx 

 should be heavier than the perfect metal ? Such a calx 



