viii PREFACE 



The Governors of the Imperial College of Science and Tech- 

 nology. 



Professor A. Liversidge. 



William Macnab, Esq., F.I.C. 



J. Lewis Major, Esq., Messrs. Major and Co., Ltd., Hull. 



Professor W. A. Noyes, University of Illinois, U.S.A. 



Professor W. J. Pope, University of Cambridge, England. 



Dr. Frederick B. Power, of the United States Department of 

 Agriculture, Washington. 



Lt.-Col. Sir David Prain, Director of the Royal Botanic 

 Gardens, Kew. 



The Society of Dyers and Colourists, Bradford. 



The Society of Chemical Industry. 



The Rt. Hon. Lord Rayleigh. 



The late Professor Sir William Ramsay. 



Sir Boverton Redwood, Bt., Adviser on Petroleum to the 

 British Government. 



Professor T. W. Richards, Harvard University, Cambridge, 

 Mass, U.S.A. 



Professor Sir J. J. Thomson, Cambridge, England. 



J. C. Umney, Esq., of Messrs. Wright, Layman, and Umney, 

 Wholesale Druggists. 



Herbert Wright, Esq., F.L.S. 



I am also indebted to my friends, Professor Morgan, Professor 

 Philip, and Dr. Martha Annie Whiteley for kindly reading 

 portions of the manuscript. 



I am under a special obligation to the Council of the Society 

 of Chemical Industry for permission to adorn the cover of the 

 book with the beautiful obverse of the medal awarded by the 

 Society every two years for discoveries or inventions or other 

 distinguished services rendered to industrial chemistry. The 

 medal was designed by Miss Margaret May Giles (Mrs. Bernard 

 Jenkin). It represents symbolically the four elements of Demo- 

 critus and Aristotle, namely, Earth, Water, Fire, and Air, 



