SOME UNSOLVED SCIENTIFIC PROBLEMS 



lowers that the molecules of sugar merely glide every- 

 where between the molecules of water, without chem- 

 ical action; or, on the other hand, dismissing this me- 

 chanical explanation, we may say with Mendeleef that 

 the process of solution is the most active of chemical 

 phenomena, involving that incessant interplay of atoms 

 known as dissociation. But these two explanations 

 are mutually exclusive, and nobody can say positively 

 which one, if either, is right. Nor is either theory 

 at best more than a half explanation, for the why of 

 the strange mechanical or chemical activities postulated 

 is quite ignored. How is it, for example, that the 

 molecules of water are able to loosen the intermolecular 

 bonds of the sugar particles, enabling them to scamper 

 apart? 



But, for that matter, what is the nature of these in- 

 termolecular bonds in any case? And why, at the 

 same temperature, are some substances held together 

 with such enormous rigidity, others so loosely ? Why 

 does not a lump of iron dissolve as readily as the lump 

 of sugar in our bowl of water ? Guesses may be made 

 to-day at these riddles, to be sure, but anything like 

 tenable solutions will only be possible when we know 

 much more than at present of the nature of intermo- 

 lecular forces and of the mechanism of molecular 

 structures. As to this last, studies are under way that 

 are full of promise. For the past ten or fifteen years 

 Professor Van 't Hoof of Amsterdam (now of Berlin), 

 with a company of followers, has made the space rela- 

 tions of atoms a special study, with the result that so- 

 called stereo-chemistry has attained a firm position. 

 A truly amazing insight has been gained into the space 



219 



