505 
tions of suitable concentration, while even a chloroform solution 
which contained 35.4°/, by weight of alloeinnamie acid, and in 
which, therefore, double molecules were certainly present, no trans- 
formation was observed after six days’ cooling. In my opinion the 
explanation of this is that only solutions containing nuclei can be 
transformed, and that there exists only one kind of double molecule. 
Van DER Waars’ supposition that double molecules consist merely 
in the temporary association of the single molecules, is thus rendered 
more probable. Further investigation is required to clear up this point. 
In the nuclei we have thus a determinate arrangement of the 
molecules. They represent the smallest particles of the substance 
in the solid condition, the simplest nucleus consisting of two mole- 
cules. It is not necessary to assume that the molecules are united 
at the carboxy! groups in order to explain the existence of different 
isomerides, since, as | have found, coumarine, which has no carboxy] 
group in the molecule, occurs also in a metastable form. It appears 
to me more probable that the reason for the occurrence of isomerides 
must be sought in the double bond. I hope shortly to return to this point. 
STOBBE and Scudnpure (p. 200) consider the occurrence of “Lösungs- 
gemische’ of the 42°- and the 68°-acid as an argument for the 
isomerism of these acids. It is clear from what has been said above, 
that the nuclei in the solution play an important part. The authors 
have however, interpreted their experiments in a different sense. 
They supposed that they had found that “In jedem Hinzelfalle als 
Verdampfungsriickstand 68°-Säure erhalten wird nach einem Gesamt- 
zusatz von 2.9-—4.1 Proz. 68°-Säure, d.h. waren weniger als 2.9 
Proz. 68°-Säure zur 42°-Säurelósung zugesetzt, so schmolz der Ver- 
dampfungsrückstand bei 42°; betrug der Zusatz mehr als 4.1° Proz. 
68°-Säure, so zeigte der Verdampfungsriickstand den Schmelzp. 68°”. 
They therefore conclude that the distillation residues are to be 
regarded as mixtures of the 42°-acid and the 68°-acid. On p. 204 
they state: “Wenn, wie oben gezeigt worden, die Lösung von der 68°- 
Säure verschieden von der Lösung der 42°-Säure ist, und wenn nach 
Zusatz von wenig 68°-Siurelésung zur 42°-Säurelösung ein bei 42° 
schmelzender Verdampfungsriickstand erhalten wird, so kann dieser 
nicht reine 42°-Siure (fest) sein. Es muss vielmehr ein Gemisch der 
beiden isomeren Sáuren sein’. It is then assumed that solid solutions 
of these forms exist, and that the erystals are mixed erystals of the 
42°-acid and the 68°-acid. It is obvious from what has been said 
above that this hypothesis is devoid of foundation. 
Also on theoretical grounds, from the point of view of the 
authors, this hypothesis is untenable. 
