525 



the tempeparatiire of the three-pha«e equilibrium hydrate -|- ji- 

 anhydride -\- solution. 



The «-moditioation appeared, therefore, to be metastable below 

 200°, and now it was the question how it is at the higher tempe- 

 ratures. The solubility lines could not be pursued towards higher 

 temperatures, because the milk sugar decomposes during the time 

 necessary for a determination. 



The only thing that offered a chance of success was the 

 determination of the melting point in exceedingly thin capillary 

 tubes, according to the method of Soch. 



This investigation gave a perfectly convincing result, for the 

 «-modification melted in 2 seconds in a bath of 222°, 8, while the 

 ^^-modification melted in the same time in a bath of 252°,2. Hence 

 the ^?- modification melted 29.4° higher than the ^^-forrn, which shows 

 that the «-modification is metastable up to its melting-point. 



On this occasion also the melting-point of the hydrate was. deter- 

 mined according to Soch's method, for which was found 201°, 6. It 

 may serve as a proof for a very small velocity of transformation 

 in the solid substance, when as here, the melting-point of a hydrate 

 is to be realised more than 100° above the already discussed dehy- 

 dration point. 



b. The hydrate is a hydrate of the a-modification. 



All this did not solve the problem offered by the milk sugar, 

 however, by any means, for another highly remarkable peculiarity 



