CHEMICAL APPARATUS AND PRODUCTS. 197 



some of the names still in use, as alembic, alkali, and alcohol, 

 containing the Arabic prefix al. 



From the time of Geber to the end of the fourteenth or middle 

 of the fifteenth century there seems to have been a succession of 

 philosophers who spent most of their energies in vainly endea- 

 vouring to discover a material that would turn all metals into 

 gold, a liquid that would dissolve everything, and a medicine that 

 would prolong life indefinitely. During their wild experiments 

 some very valuable discoveries were, however, made, but most of 

 them were described in such an enigmatical manner that it is 

 extremely difficult to understand their meaning, or, indeed, if 

 they have any meaning at all. The belief in the transmutability 

 of metals existed till the end oi the seventeenth century, and even 

 as late as 1721 an alchemical experiment is gravely recorded. 



From Geber to Boyle, who has been termed the father of modern 

 Chemistry, many most important isolated discoveries were made, 

 and materials were thus prepared for a comprehensive theory, the use 

 of which was delayed by the prevalence of scholastic speculations. 



Towards the close of the seventeenth century, Stahl, who died in 

 1734, developed, from the suggestions of Beccher, a methodical 

 theory of Chemistry. This was the theory of Phlogiston, which was 

 held by chemists for nearly a century. According to this theory, all 

 combustible bodies contain a peculiar principle named phlogiston, 

 and it is the escape of this principle which causes flame. These 

 chemists showed that the burning of combustible bodies, and the 

 changes which some metals undergo when heated in air (or calcina- 

 tion), are processes of the same order, and Stahl described several 

 experiments which indicated that the escape of phlogiston took 

 place under these conditions. When phosphorus and sulphur are 

 burnt products are formed which when dissolved in water possess 

 the characters oi acids, whilst metals, such as lead, zinc, and iron, 

 when submitted to calcination, give rise to earthy bodies called 

 calces. When a calx, such as that of lead, is heated with a combus- 

 tible substance like charcoal, metallic lead is reproduced ; it was 



