54 SECTIONAL ADDRESSES. 



the provision of a special type of balance, have been tried in many- 

 laboratories, and have found favour, it is understood, in several of them, 

 more particularly abroad. But the general experience has been that the 

 technical skill required to obtain good results is acquired only after long 

 practice, and that whereas the methods are useful for gaining an indication 

 of structure when the quantities of material at hand are so small as to 

 necessitate their use, yet when a sufficient quantity of substance is available 

 the older methods are more reliable and more easily carried out. It is 

 interesting to note that the new methods which have been introduced by 

 Prof, ter Meulen, of Delft, are going to be described to us by Prof, ter Meulen 

 himself, who is fortunately with us at this meeting. Prof, ter Meulen will 

 give an account of his methods on Tuesday morning, and they will be 

 shown in actual operation during the soiree on Tuesday evening. Chemists 

 will then see that a great saving of time can be effected by methods which 

 can not only be used to analyse the small quantities employed by Pregl, 

 but also quantities of 0.1 grm., such as organic chemists have been accus- 

 tomed to use in the past, and which have been shown to produce the most 

 accurate results. 



The Utilisation of Forest Products. 



The immense number of organic compounds distributed among the 

 plants, trees, and grasses which form the forests and jungles of the world 

 offer a wide field for research which has still much to yield. Our know- 

 ledge of the medicinal properties of organic substances and the various 

 uses to which they could be put in the service of mankind did not come 

 to us through any effort of the chemist, but as the outcome of a process 

 of trial and error which is as old as the human race itself. These products 

 were obtained from vegetable materials present in the forests, and as 

 time went on they were extracted in a form possessing some degree of 

 purity, and the plants containing those with specially valuable properties 

 were cultivated for their production. As soon as a theory of organic 

 structure was evolved upon which prediction could be based, these useful 

 products were subjected to close investigation, and in several cases they 

 were prepared by laboratory means. As an outcome several of them, such 

 as indigo and alizarine, were found to be capable of production more 

 economically by the chemical method than by the processes of life, and 

 the natural substances were rapidly replaced by the artificial products. 

 Others still resist all efforts to unravel their structures, and remain still 

 unsynthesised. Nevertheless it has been by a study of the chemical 

 structure of natural products that much has been learnt regarding the 

 relation between chemical composition and physiological action, and 

 although it may not have been found possible economically to prepare 

 the natural substance itself, the clue revealed by the determination of 

 structure has led to the production of other substances which have not 

 only shown the properties of the natural compound in an enhanced form, 

 but have also exhibited other valuable physiological effects. The 

 determination of structure has, therefore, two objects — to prepare the 

 natural substance and to ascertain the particular arrangement of the 

 atoms in the molecule which confers on it the properties which determine 

 its value. The determination of the striicture of indigo led not only to 



