Diatomaceous earth is a naturally occurring, soft, powdery substance derived from the fossilized remains of single-celled algae called diatoms. Its unique microscopic structure directly influences its properties and applications. Understanding its appearance under magnification reveals why it behaves as it does.
The Microscopic Appearance of Diatomaceous Earth
Under a microscope, diatomaceous earth appears as an intricate collection of tiny, glass-like silica shells called frustules, which are the fossilized remains of diatoms. These frustules are often a mixture of whole and broken fragments. They exhibit remarkable diversity in shape, primarily falling into two categories: centric and pennate.
Centric diatoms are circular or disc-shaped, often resembling ornate wheels. Pennate diatoms are elongated, appearing like miniature boats or needles. Both forms display delicate, symmetrical patterns, including pores, ridges, and spines, which vary significantly between different diatom species. These elaborate structures, composed of hydrated silicon dioxide, give diatomaceous earth its distinctive appearance and properties.
Preparing a Slide for Viewing
To observe diatomaceous earth under a microscope, preparing a simple wet mount slide is an effective method. The necessary materials include a clean microscope slide, a coverslip, a small amount of diatomaceous earth powder, and a dropper bottle of water.
Begin by placing a single drop of water in the center of the microscope slide. Using a toothpick or a very small spatula, transfer a tiny amount of diatomaceous earth into the water drop and gently mix it to disperse the particles. Carefully lower a coverslip over the water and diatomaceous earth mixture. A standard compound light microscope is sufficient, and the distinctive shapes of the frustules are visible even at 100x magnification.
How Structure Relates to Function
The unique microscopic structure of diatomaceous earth directly influences its practical applications. The sharp, abrasive edges of the silica frustules, clearly visible under magnification, are responsible for its effectiveness as a physical insecticide. These microscopic shards can scratch and damage the waxy outer layer, or exoskeleton, of insects, leading to dehydration.
The highly porous nature of the diatom shells contributes to its utility as a filtration medium. The intricate network of pores and channels within the frustules creates a vast surface area, allowing diatomaceous earth to trap fine particles and impurities when liquids pass through it. This structural characteristic makes it valuable in processes like water purification and beverage clarification.