ARABIC CHEMISTRY 257 



accidental qualities, that is, qualities which are not essential 

 to the metallic species and which may be removed by proper 

 treatment. " Imperfect " metals are often compared to a 

 man suffering from illness : if the illness be removed by adminis- 

 tration of an appropriate drug, or in some other way, the sick 

 man returns to his normal state of health. 



The possibility of the transmutation of the metals is logically 

 required by this theory, and it is interesting to remember that 

 we have reached very much the same position in chemical 

 theory to-day. The difference is, of course, that we have an 

 incomparably fuller knowledge of the structure of matter 

 than the mediaeval chemists had, and believe that no ordinary 

 chemical reaction can ever bring about appreciable trans- 

 mutation. But it is difficult to imagine what other theory 

 could have inspired chemistry and encouraged chemical 

 research in the early Middle Ages so much as that of the 

 Transmutation of the Metals. It will be seen, too, that this 

 theory was not the fundamental theory of chemistry : it has 

 acquired that reputation solely because it represented the 

 most important and practical problem of chemistry that the 

 alchemists set themselves. The possibiHty of transmutation 

 was by no means universally beheved in by mediaeval Arabian 

 chemists. Avicenna vehemently opposed it, and we find many 

 criticisms of it quoted by both Ibn Khaldun and Hajji Khalifa. 

 These criticisms no doubt proved a useful spur to further 

 experimental work and modifications of theory. But had 

 they been accepted and the theory of transmutation abandoned, 

 it is probable that the development of chemistry would have 

 been greatly retarded. 



The details of the methods employed to perfect " imperfect " 

 metals vary considerably from time to time, and from chemist 

 to chemist, but the general feeling appears to be as follows. 



Fire alone may possibly be sufficient, but there are practical 

 difficulties to be overcome, and these prove to be insurmount- 

 able. The alternative is to prepare a substance which, in our 

 modern phrase, will act as a catalyst on the reaction, or which 

 will restore the balance of the imperfectly adjusted metal and 

 so bring it to perfection — hence alchemy is sometimes called 

 the " science of the Balance " : the name must not be taken 

 as referring to a machine for weighing, although the alchemists 

 were as a rule very careful to insist upon accurate weighing. 



Gold was considered to be in a state of perfect equilibrium, 

 while the other metals differed from it by excess or deficiency 

 of certain constituents. The problem then was to find a 

 substance which would remove the excess or make up the 

 deficiency, and this substance was called the Elixir (Al-Iksir) 

 or the Philosopher's Stone. It was usually thought that no 



