1. A study was made of the catalytic dimerization of five oiefins, namely C10-C19 trisubstituted ethylene derivatives, and the products of the hydrogenation of these dinners were prepared. 2. In the course of the dimerization partial isomerization of the dimers occurred. 3. The calculated densities of the resulting C20-C38 isoparaffins of type (in which R=propyl, butyl, pentyl, hexyl) are extremely close to the experimentally found values. Increase in the length of the side group in isoparaffins of this type from 3 to 6 carbon atoms has no substantial effect on the change in their density and freezing point. 4. With increase in the molecular weight of the isoparaffins obtained there is a sharp increase in their viscosity.