Annual Report of the Coimcil. xxxiir 



The experimental work which he published was chiefly in 

 the region of organic chemistry. An important reaction which 

 he discovered, is that in which an aromatic aldehyde is converted 

 by treatment with caustic potash into the corresponding acid 

 and alcohol : benzaldehyde, for instance, yields benzoic acid 

 and benzylic alcohol. One may mention also the series of 

 researches which he carried out on santonin and its derivatives. 



Cannizzaro was greatest as a teacher of chemistry. At the 

 time he began his career the science was in a chaotic state. The 

 objection to the atomic theory, as that theory was understood 

 between the years 1808 and i860, was that the chemical 

 formulae of substances and the atomic weights of the elements 

 were decided in tin arbitrary way. Thus there had arisen 

 three great systems of chemical formula, each with much in its 

 favour, that of Berzelius, that of Gmelin, and that of Gerhardt 

 and Laurent. The attempts which were made at compromise 

 between these different systems only resulted in heightening 

 confusion. 



Cannizzaro's contribution to the philosophy of chemistry, 

 which must make his fame enduring, was that he showed how to 

 avoid all this confusion. He described his system of chemistry, 

 though not till he had tested it amongst his own students, under 

 the title, " Sketch of a Course of Chemical Philosophy." * His 

 method was to use the hypothesis of his countryman, Avogadro, 

 as a means of arriving at the molecular weights of substances, 

 v;hether elementary or compound, and to make the molecular 

 weights thus obtained the basis for determining the atomic 

 weights of the elements. The other atomic weight methods, 

 specific heat, isomorphism, and chemical analogy were, as he 

 showed, simply auxiliary methods. 



In i860, two years after the publication of these ideas, a 

 conference of chemists met at Carlsruhe for the express purpose 

 of considering the state of confusion into which chemistry had 



* II Niiovo Ci/uento, vol. 7, pp. 321-366, 1858. Translated in No. iS 

 of the Aletnbic Club Reprints. 



