PHLOGISTON THEORY IN CHEMISTRY 



bodies, were considered compounds by the phlogistians, 

 and they believed that the calcining of a metal was a 

 process of simplification. They noted, however, that 

 the remains of calcination weighed more than the 

 original product, and the natural inference from this 

 would be that the metal must have taken in some 

 substance rather than have given off anything. But 

 the phlogistians had not learned the all-important 

 significance of weights, and their explanation of 

 variation in weight was either that such gain or loss 

 was an unimportant "accident" at best, or that 

 phlogiston, being light, tended to lighten any sub- 

 stance containing it, so that driving it out of the 

 metal by calcination naturally left the residue heavier. 

 At first the phlogiston theory seemed to explain in 

 an indisputable way all the known chemical phenom- 

 ena. Gradually, however, as experiments multiplied, 

 it became evident that the plain theory as stated by 

 Stahl and his followers failed to explain satisfactorily 

 certain laboratory reactions. To meet these new 

 conditions, certain modifications were introduced from 

 time to time, giving the theory a flexibility that would 

 allow it to cover all cases. But as the number of in- 

 explicable experiments continues! to increase, and new 

 modifications to the theory became necessary, it was 

 found that some of these modifications were directly 

 contradictory to others, and thus the simple theory 

 became too cumbersome from the number of its modi- 

 fications. Its supporters disagreed among themselves, 

 first as to the explanation of certain phenomena that 

 did not seem to accord with the phlogistic theory, and 

 a little later as to the theory itself. But as yet there 



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