14 PRINCIPLES OF CHEMISTRY 



Having accepted the truth of the above law, the question in- 

 voluntarily arises whether there is any limit to the various chemical 

 transformations, or are they unrestricted in number that is to say, is 

 it possible from a given substance to obtain an equivalent quantity of 

 all other substances ? In other words, does there exist a perpetual and 

 infinite change of one kind of material into all other kinds, or is the 

 cycle of these transformations limited ? This is the second essential 

 problem of Chemistry, a question of quality of matter, and one, it is 

 -evident, which is more complicated than the question of quantity. It 

 cannot be resolved by a mere superficial glance at the subject. Indeed, 

 on seeing how all the varied forms and colours of plants are built up from 

 air and the elements of the soil, and how metallic iron can be transformed 

 into dyes, such as inks and Prussian blue, we might be led to think 

 that there is no end to the qualitative changes to which matter is 

 susceptible. But, on the other hand, the everyday experiences of life 

 compel us to acknowledge that food cannot be made out of a stone, or 

 gold out of copper. Thus a definite answer can only be looked for in 

 a close and diligent study of the subject, and the problem has been re- 

 solved in different ways at different times. In ancient times the 

 opinion most generally held was that everything visible was composed 

 of four elements Air, Water, Earth, and Fire. The origin of this 

 doctrine can be traced far back into the confines of Asia, whence 

 it was handed down to the Greeks, and most fully expounded by 

 Empeclocles, who lived before 460 B.C. By accepting so small a 

 number of elements it was easy to arrive at the conclusion that the 

 cycle of chemical changes was, if not infinite, at all events most exten- 

 sive. This doctrine was not arrived at by the results of exact research, 

 but was only founded on the speculations of philosophers. It appa- 

 rently owes its origin to the clear division of bodies into gases (like 

 air), liquids (like water), and solids (like the earth). It seems that 

 the Arabs were the first who tried to solve the question by means of 

 experiment, and they introduced, through Spain, the taste for the 

 study of similar problems into Europe, where from that time there 

 appear many adepts in chemistry, which was considered as an unholy 

 art, and called * alchemy.' As the alchemists were ignorant of any 

 exact or strict law which could guide them in their researches, they re- 

 solved the question of the transformation of substances in a most varied 

 manner. Their chief service to chemistry was that they made a 

 number of experiments, and discovered many new chemical trans- 

 formations ; but it is well known how they solved the fundamental 

 problem of chemistry. Their view may be taken as a positive acknow- 

 ledgment of the infinite transmutability of matter, for they aimed at 



