Chapter VI 



THE GROWTH OF CHEMICAL IDEAS 



The fundamental principles of chemistry date not from 

 the seventeenth but from the end of the eighteenth and the 

 beginning of the nineteenth centuries. The delay in the 

 development of chemistry may be ascribed to two different 

 causes. The minor one is that experimental chemistry de- 

 mands access to equipment and materials to a much greater 

 extent than experimental physics. Galileo and Newton were 

 able to conduct experiments with very little apparatus in 

 ordinary buildings, and even in the nineteenth century Lord 

 Rayleigh w^as famous for the skill with which he made ob- 

 servations of the greatest precision with apparatus W'hich he 

 had constructed from pieces of wire, w^ood, and sealing wax. 

 But chemistry is the study of reactions, and it is necessary to 

 have materials which react and then to place them in suitable 

 environments, as, for instance, by heating them. Today we 

 take for granted a supply of pure chemical reagents, and we 

 can use very convenient methods of applying heat by gas 

 burners or electric furnaces. In the days when there were 

 no electricity and no gas, heat could be obtained only by 

 burning wood or coal, and no supply of suitable heatproof 

 glassware was available. It was necessary for the chemist in 

 most cases to prepare his own materials, and these were 

 usually very impure. Within our o^vn lifetime, indeed, work 

 in organic chemistry has been delayed by the inaccessibility 

 of starting materials and has only recently been facilitated by 

 their supply. A second and more important cause of the 

 delay in the advance of experimental chemistry was that it 

 got off to a wrong start twice. The earliest chemists were 



alchemists, who were attempting to find the philosophers' 



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