Hence, if by alloying certain metals they obtained a metal resembling gold in color, this was perhaps really an approach to making gold, and, if it had been possible to make such an alloy by any combination of materials as should answer all their known tests for gold, from their standpoint it might well be real gold.
We can comprehend that if we considered an element only as a combination of certain qualities and not as a specific simple substance—there would be no a priori improbability in such an hypothesis.
Thus the experience of the chemists with the metals was the real motive force in vitalizing and in modifying the ideas of the Greek philosophers with respect to the nature of matter and its changes. The attempt to imitate precious stones was another line of work which helped to confirm these theories, though it may well be doubted whether in all cases the alchemists were self-deceived as to their success in producing the real articles even when they succeeded in passing them off as genuine.
Nevertheless the accepted theory of the essential unity of matter and of the possibility of transmuting one element or substance into another was the working hypothesis that kept the alchemists, for so many centuries, at their vain labors. As the study of the metals and their uses formed so large a part of chemical activity, there also grew up in time special theories as to the origin and changes of metals. One of the oldest of these can also be traced to the Egyptians and to Plato—the notion that mercury bears a peculiar relation to the origin of the metals. Among the Egyptians lead occupied a similar position, but the substitution of mercury in this role took place as early as Plato.
The very peculiar properties of mercury—argentum vivum, the liquid living silver, quick-silver—and the strange manner in which it lost its identity in combination and in alloys with other metals gave rise to a theory that it was the source of the other metals. And again, as with other metals, it might not always be the same in composition and properties, the idea developed that not the ordinary mercury, but a mystical purified mercury—the so-called "mercury of the philosophers" was a constituting element in all the metals.
So also sulphur bore a prominent relation to the occurrence and to the furnace reactions of metallic ores. Its combustibility, its frequent presence in metallic ores, the combinations with metals and the colors of these combinations—the red or black of its mercury combinations—the black copper compound—the yellow or red of arsenic compounds—etc., endowed it also with a mysterious relation to the metals, and it also became considered as a constituting element of the metals. Arsenic, which acts very similarly to sulphur in many such compounds, was sometimes associated with it in that role. And here again was assumed not ordinary sulphur, but a fancied perfect sulphur—the "sulphur of the philosophers."
