although they noticed plainly the close relationship. RemwKe, who in 
1879 discussed *) the analogy and observed it more keenly than any 
one before him, evidently still hesitated — as in fact all his con- 
temporaries would have done — to assume that mésechility should 
exist in the so/id condition. 
But the development of physical chemistry in the last twenty-five 
years has removed this difficulty. In 1890 Var *r Horr published his 
celebrated theory of the solid solutions, which shows that miscibility 
exists in the solid condition just as well as in the liquid state, and 
the cases have become almost innumerable where this miscibility 
has been actually observed. In consequence, the difficulty of the 
older writers has been removed and now, I ask, what can still 
prevent us from assuming that swelling means mixing *), in other 
words that when a solid substance swells in water, this depends on 
the formation of a solid solution of water in the imbibing body *). 
Of great significance to the problem of imbibition, seems to 
me to be TamMann’s idea *) that amorphous solid substances are in 
many cases nothing but liquids of very great viscosity. TAMMANN 
showed that all possible liquids, if they are cooled rapidly enough 
to prevent crystallisation, become gradually more and more viscous 
and are converted, without any discontinuity, into solid amorphous 
bodies ; known instances of this are glass, cane-sugar, g@lycerin. 
This view, also warmly defended by Bakutts RoozeBoom and O. 
LEHMANN, throws a remarkable light on the fact that the sub- 
stances of unlimited imbibition power (which are all amorphous), 
when absorbing water, are converted continuously into aqueous 
solutions. It leads us to the hypothesis that amorphous swelling bodies 
are substances of so great a viscosity that they practically possess the 
solid aggregation condition, but have still retained their miscibility 
with water. 
If this hypothesis is correct the swelling of a piece of gelatin and 
the water absorption of such liquids as sulphuric acid and glycerin 
1) Loe. cit. p. 123—128. 
*) The substances of limited imbibition power would then be analogous to 
those of limited miscibility, those of unlimited imbibition power to those of un- 
limited miscibility. Limited and unlimited miscibility are not different properties; 
in substances with a crilical mixing point both pass into each other at a change 
of temperature. 
*) Similar hypotheses have been propounded repeatedly by physico-chemists. 
But they have not worked out this supposition any further, to ascertain whether 
it can be used as a working hypothesis in the investigation of the quantitative 
laws of the imbibition power. 
*) Compare Zeitschr. f. physikal. Chem. 25, p. 469—479, 
