Donald Anthony
Citric Acid, 2004

Photomicrograph; Zeiss microscope with polarizing light filters; Nikon 5000 digital camera

Peterborough, Ontario, Canada

Citric acid is a natural preservative that is found in citrus fruits or can be synthetically manufactured in the lab. It is often used to produce acidic or sour tastes in foods and soft drinks. For this photomicrograph, citric acid powder was dissolved in water and dried rapidly on a clear slide to form crystals. The crystals were then photographed using a microscope equipped with a series of polarizing filters that revealed the internal colors, or birefringence, associated with this compound when examined under polarized light. When energy is polarized, it is all oscillating in the same orientation. When two polarizing filters are oriented at 90 degrees to one another, all incident energy is subtracted from the system. When a material that contains multiple refractive indices is viewed in this system, the various components may appear as different colors.

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