PHLOGISTIC THEORY. 



with a distinctness which Beccher did not attain. In 1697, appeared 

 Stahl's Zymotecknia Fundamentulis (the Doctrine of Fermentation), 

 " siinulque experimcntum novum sulphur verum arte producendi." In 

 this work (besides other tenets which the author considered as very 

 important), the opinion published by Beccher was now maintained in 

 a very distinct form ; namely, that the process of forming sulphui 

 from sulphuric acid, and of restoring the metals from their calces, are 

 analogous, and consist alike in the addition of some combustible ele- 

 ment, which Stahl termed phlogiston ($>Xoyi'oVov, combustible"). The 

 experiment most insisted on in the work now spoken of, 2 was the for 

 mation of sulphur from sulphate of potass (or of soda) by fusing the 

 salt with an alkali, and throwing in coals to supply phlogiston. This 

 is the " experimentum novum." Though Stahl published an account 

 of this process, he seems to have regretted his openness. " He denies 

 not," he says, " that he should peraclventure have dissembled this 

 experiment as the true foundation of the Beccherian assertion con- 

 cerning the nature of sulphur, if he had not been provoked by the 

 pretending arrogance of some of his contemporaries." 



From this time, Stahl's confidence in his theory may be traced becom- 

 ing more and more settled in his succeeding publications. It is hardly 

 necessary to observe here, that the explanations which his theory gives 

 are easily transformed into those which the more recent theory supplies. 

 According to modern views, the addition of oxygen takes place in the 

 formation of acids and of calces, and in combustion, instead of the 

 subtraction of phlogiston. The coal which Stahl supposed to supply 

 the combustible in his experiment, does in fact absorb the liberated 

 oxygen. In like manner, when an acid corrodes a metal, and, accord- 

 ing to existing theory, combines with and oxidates it, Stahl supposed 

 that the phlogiston separated from the metal and combined with the 

 acid. That the explanations of the phlogistic theoiy are so generally 

 capable of being translated into the oxygen theory, merely by invert- 

 ing the supposed transfer of the combustible element, shows us how 

 important a step towards the modern doctrines the phlogistic theory 

 really was. 



The question, whether these processes were in fact addition or sub- 

 traction, was decided by the balance, and belongs to a succeeding period 

 of the science. But we rnay observe, that both Beccher and Stahl 

 were aware of the increase of weight which metals undergo in calcina 



2 P. 117. 



