526 



presented itself for the hydrate, a peculiarity which as far as we 

 know, has never yet been observed for another hydrate, though it 

 is probable that it will occur in more cases. 



We found, namely, that the hydrate when lieated at 125° in dry 

 condition, always yields the «-modification, whereas in presence of 

 the saturate solution the hydrate at the same temperature always 

 passes into the /^-modification. 



To study this interesting pheijomenon more closely the hydrate 

 was brought in contact with a vessel of strong sulphuric acid of 

 ordinary temperature at temperatures between 0.5° and 200° in 

 vacuum. It appeared in all these experiments that the hydrate was 

 exclusively converted to the «-anhydride, and this happened both 

 below and above 93°. 5. 



This result enables us, as we shall see presently, to consider the 

 milk sugar problem from another point of view, which will make 

 it possible to account for all the phenomena observed up to now 

 in the system water-milk sugar in a simple way. 



Hudson already assumed the transformation : 



hydrate ^ /?+ H,0. 



In this the expectation that the hydrate is a hydrate of the ^• 

 modification is of course implied. 



Now Hudson assumes further that the water in the hydrate is 

 bound in this way 



/OH 

 -C-OH 



\h 



.from which would follow that the hydrate might just as well be 

 called a hydrate of the ^^-modification as a hydrate of the /?-modi- 

 fication, because the stereochemical difference in the final carbon 

 atom, which he assumed for the ;?- and ji- modifications '), viz. 



H-C— OH and HO— C— H 

 A A 



has perfectly disappeared in the structure formula for the hydrate. 

 If this were so the hydrate would be neither a- nor /3-hydrate 

 and then it could absolutely not be understood why the dry hydrate 

 always gives «-anhydride, also above 93°, whereas the damp hydrate 

 passes into /?-an hydride above 93°. 



We must, therefore, certainly reject this supposition ; the hydrate 

 must be a hydrate of « and /^-anhydride, and now all the experi- 



1) h Amer. Cheïfl. Soc. 31 66 (1909). 



