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The interferential method is presented for detcrmining the inclination angle 8 of molecules in homogeneously ordered plane-parallel liquid crystalline layers. The essence of the method is the analysis of the changes in the layer transmission caused by the change in conditions of interference. The angle 8 is calculated from the exact, explicit relation where from no limitations the size of the angle results. The measuring-stand is described that enabled the method to be put into practice. The results for the PCB layer are presented by way of example.

The spacings of t h e smectic layers are compared with t h e lengths of molecules of p-substituted phenyl 4-(trans-4'-n-decylcyclohexyl) benzoattes. It has been found t h a t if the NO,, CN or CHO groups are substituted in the p-position of t h e phenyl, then t h e smectic layers consist of dimers, whereas in the presence of the NCS, COCH,, T, C1, Br, F substituents the srnectic layers reveal a monomolecular spacing.Die nicken der smektischen Schichten wurden mit der Molekulliinge von 4-(trans-4'n-llecylcyclohexyl) benzoaten dem p-substituierten Phenyl verglichen. Es wurde festgestellt, da13, wenn als p-Substituent im Phenyl eine der folgenden Gruppen NO,, CN, COH vorliegt, sich die smektischen Schichten aus Dimeren zusammensetzen, dagegen sind in Anwesenheit von den Substituenten NCS, COCH,, J, CI, Br, F die smektischen Schichten an GroRe dem einzelnen Molekul gleich. __