527 



merits made by us, in which it was found that the hydrate in dry 

 condition gives the «-anhydride at all the temperatures examined 

 point to this that the milk sugar hydrate is the hydrate of the 

 a-modijication. 



c. The hydrate presents a transition-dehydration- point. 



This conclusion throws another light' on the problem : the trans- 

 formation point of 93°. 5 is no ordinary transformation point, for in 

 this point takes place the conversion 



«-hydrate — ^ ^-anhydride, + solution. 



If we had to do here with an ordinary transformation point, the 

 conversion would be the following : 



«-hydrate •^— «-anhydride + solution. 



For milksugar, hoiuever, the dehydration is accompanied with a 

 transition of the ct-modifcation into the {i-forin, so that here a pheno- 

 menon is met with, which as far as we know, has never been 

 observed as yet. To express this particular behaviour also in the 

 denomination of the transformation point we shall call this point 

 henceforth the transformation-dehydration point, resp. transition- 

 hydration point. 



d. The system water-milksugar must be considered as pseudo- 

 ternary. Derivation of the isotherm-diagram. 



This remarkable result must be expressed in our way of repre- 

 sentation of the sj'Stem considered here. 



A.S the occurrence of the said transition-dehydration point shows 

 with the greatest clearness that we must consider the system water- 

 milksugar as pseudo-ternary, we have begun collecting data for the 

 representation of the solubility-isotherms of the system H,0 -f- «-'"ilk- 

 sugar -f- /:f-milk-sugar at a temperature below 93°. 5. 



In fig. 4 the points a and b indicate the initial-solubility of the 

 hydrate «„,/ and of the (i-an hydride determined by Hudson ^) at the 

 temperature of 0°. The three-phase-equilibrium «„^ -\- ^ -\- h was not 

 determined, and was found by us by starting from these three phases, 

 and by squirting off the liquid through a filter after 1 hour's vigorous 

 stirring. The total concentration of this liquid was determined 

 by evaiioration and weighing, i.e. the total quantity of milksugar. 

 In this way we find, therefore, on what line drawn parallel to the 

 line «i?, the point D lies. In order to be able to indicate the place 

 of the point D on this line, a second quantity was pressed through 

 a filter, and then through a bent tube provided with a refrigerator, 

 through which water flowed of the same temperature as that of the 



1) J Amer. Ghem. Soc. 30 1767 (1908). 



