Caption

Scanning electron micrograph (SEM) of BDH Analar sodium chloride, or pure salt, recrystallised from distilled water. The crystal is built up from a cubic lattice of sodium & chloride ions. In the absence of impurities an exact cubic crystal is formed. This micrograph shows that in practice the basic cube is often disrupted by dislocations, giving rise to crystals with a wide variety of shapes although they retain the underlying cubic symmetry. Magnification X 350 at 8x10 size, X 42 at 35mm size.