100 
side of this very asymmetrically situated region of unmixing just 
such a line as was deseribed just now. 
No doubt we are not justified in concluding from this agreement 
that the substances to which Mr. Karz’s figures refer, satisfy all the 
conditions that we had to put in order to be able to arrive at our 
conclusions ; to apply the law of corresponding states to casein and 
haemoglobin must certainly be called a very bold generalisation, 
even apart from the other suppositions on which our formulae are 
founded. Still I thought this agreement striking enongh to justify a 
closer investigation for the solution of the question in how far the 
experimental particularities found by Mr. Katz would have to be 
expected in virtue of the simplest theory for a mixture of two per- 
fectly normal components, when the ratio between the size of the 
molecules, %/,,, becomes very great. Mr. Katz was so kind as to 
summarize the results of his measurements for me as follows: 
1. If we draw the water-vapour tension of the swelling substance 
as function of the molecular percentage (vaN DER WAALS’s p, v-curve), 
we get a line which (ef. fig. 1, which represents the line for inulin 
in proper proportions *)): 
a. lies for not very small values of # (pure water) under the 
value which the vapour tension would have if van ’rT Horr's law 
p=p, — 2) held for all concentrations. 
b. begins almost horizontally for « about 1, and does not begin 
to rise abruptly until past «= ‘'/,. 
c. turns its convex side downward for a about 1, then gets a 
point of inflection (for smaller z), and finally turns its concave side 
downward for very small value of «. 
d. presents an excentrically situated region of unmixing for very 
small x, so excentrically as has not been observed anywhere else as 
yet. Pretty well pure water «= 0.00001 coexists with z = 0.002 or 
0.006. The lines for casein (albumen) and inulin (polysaccharide) may 
serve as an example. For both substances the minimum molecular 
weights have been taken (casein = 4000, inulin = 1800) in all these 
calculations. If higher values are used, the above-mentioned properties 
are even more pronounced. 
1) In this figure of Mr. Katz the component with the smaller molecule (water), 
has, however, been thought on the right hand, whereas in the text it has been 
assumed, where the contrary has not been expressly stated, that the molecular 
weight increases from left to right. 
