Lattices and Symmetry of the Unit Cells

Asymmetrical molecules occur very frequently in organic chemistry. We would, at first, be inclined to expect, therefore, that the triclinic crystal system would be frequently met with, but actually nearly all asymmetrical molecules crystallize in the monoclinic system their lattices possess diagonal screw axes or slip-surface planes of symmetry. 

An explanation can be found in this way for the phenomenon well known in organic chemistry that both rate of crystallization and crystallizing power may greatly differ from solvent to solvent. It may be cited as an example that the higher dibasic acids crystallize from water in laminae but from hydrocarbons in quite long, thin needles, because in water the lipoid chains, as in the paraffins, promote the production of laminae, whereas in benzene the differing solvation relationships cause the produc- 

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