Abstract: The invention relates to liquid crystal nematic substances for electro-optical devices for the modulation of light, for the reproduction of numerals, signs and images as well as an orienting medium for spectroscopy and gas chromatography.It was found that compounds containing two or three rings, connected by carboxyl groups are new liquid crystal nematic substances of the general formula ##STR1## where R.sup.1 =C.sub.n H.sub.2n+1, CN; R.sup.2 =C.sub.m H.sub.2m+1, CN;R.sup.3 =H, CH.sub.3, C.sub.2 H.sub.5 Cl, Br; x=0 or 1; m,n=numbers from 1 to 10 are suitable for electro-optical arrangements for the modulation of transmitted or reflected light as well as for the reproduction of numeral signals and images, and further, as an orienting medium for spectroscopy and gas chromotography.Other liquid crystal substances or non-liquid crystalline substances, particularly dyes, may be added to the substances according to the invention.