PKEFACE xi 



tabular form by placing the elements in series, groups, and 

 periods, two such tables are given at the end of this preface. 



In this fifth edition I have not altered any essential feature of 

 the original work, but have enlarged it in two directions. First, 

 the doctrine of chemical equilibria, originally introduced by 

 Berthollet and Henri Sainte-Claire Deville, is discussed more 

 fully and minutely than in the earlier editions, as it has during 

 recent years been established on a much firmer footing; and, 

 second, the descriptive data referring to the elements have been 

 increased by many new facts. 



D. MENDELEEFF. 



