A tiny amount of sulphur (several milligrams) was mixed with various organic compounds, including acetanilide and urea, and carefully melted under a cover glass. After melting, the preparation was quickly removed from the hotplate and the cover was pressed down firmly before any of the constituents could recrystallize (to reduce the thickness of the preparation). The objective was a plan apochromat 4x/0.16 NA coupled with a low power achromatic condenser. The microscope was a Zeiss Ultraphot III equipped with an automatic 35-millimeter photohead. The film was Fujichrome Velvia. (10x)