18'^ 



As to the connexion existing l)etwcen «- and /?-Storax finnamie 

 acid, notliing is as yet iinown witli certainty. 



Tiie occurrence of dilferently crystallised forms of a substance 

 may he generally attributed to polymerism, isomerism or polymorphism. 



In the first case the one form is a polymeride of the other and 

 thus possesses a double or multiple molecular weight, in the second 

 case the molecular weight is the same but the structure of the 

 molecule is different, whereas in the latter case where the difference 

 exists only in the solid condition and disappears both in the liquid 

 and the gas the arrangement of the molecules in the "Raumgillcr" 

 is accepted by some as the cause of the difference whilst otiiers 

 think that in this case also, a ciicmical difference between the solid 

 forms is very probable '). 



There has been no lack of efforts to determine the connexion 

 between the different forms of the cinnamic acids. 



According to Erlenmeyeu Jr.') there exist eight forms of cinnamic 

 acid, namely four of the normal and four having as type ^//ocinnamic 

 acid. The first four appertain to each othei' two and two and 

 according to Eri.enmeyi':!}, these pairs should exhibit differences in 

 the benzene nucleus. 



Among the four rr//(*acids we find mentioned, in addition to the 

 three known acids, also a triclinic cinnamic acid, which he noticed 

 a few times during his research, but of which the mode of formation 

 is as yet quite obscure. ERLENMEirR sees in the different crystallised 

 forms different chemical substances and endea\ours to explain this 

 case of isomerism. 



I cannot find his eiïort, which he iiim.seif wishes to be looked 

 upon as a sl-etcli, a very happy one. 



He reverts to the antiquated idea where the properties of a double 

 bond are explained by the presence of a single bond and free affini- 

 ties or as some express it, unoccupied affinity positions. Then, he 

 assumes that on turning one of the two carbon tetrahedrons, between 

 which the double bond exists, three different metastable forms can 

 occur dependent on the different position of the groups on the one 

 carl)on tetrahedron in regard to that of the other one. In this manner 

 he arrives at six different forms all capable of occurring in left- and 

 riglit-handed modifications. Three thereof belong to the type of the 

 normal cinnamic acid and three to that of the <7//oacid. 



1) 0. Lehman writes in "Die neue Welt der fliissigen Krislalle" 1911 p. SI: 

 "daraus folgt aber lediglich, dass diese chemischen Methoden nicht ausreiihend 

 sind, jede Verschiedenheit der Moiekiile zu entdecken und dass man polymorplie 

 Modifikationen nicht oline weiteres als chemisch idenlisch betrachten darf." 



-) liiochem. Z.eitschrifl 35, 149 (1911) and following. 



