Cadmium (Cd) is a soft, silvery-white heavy metal found in Group 12 of the periodic table, often associated with zinc ores. This element is highly valued in industrial processes due to a set of unique physical properties, including its relatively low melting point and excellent resistance to corrosion. Understanding the thermal properties of this metal is the first step toward appreciating both its widespread utility in modern technology and the significant health and environmental concerns it poses.
The Specific Melting Point
The temperature at which Cadmium transitions from a solid to a liquid state is 321.07 degrees Celsius. This value represents the point where the solid and liquid phases of the metal exist in equilibrium under standard atmospheric pressure. In other common temperature scales, the melting point is equivalent to 609.93 degrees Fahrenheit and 594.22 Kelvin. This relatively low melting point makes Cadmium commercially useful in certain metallurgical applications.
Characteristics and Industrial Role
Cadmium is a malleable metal known for its resistance to chemical corrosion and high temperatures. These attributes, combined with its low melting temperature, allow for easy alloying and application in protective coatings. The largest industrial use for Cadmium is in the manufacturing of rechargeable nickel-cadmium (NiCd) batteries, where it serves as the anode material. These batteries are valued for their long life and dependable performance in portable power tools and emergency lighting systems.
The metal is also used in electroplating, where a thin layer of Cadmium is applied to steel, iron, and other alloys to protect them from rust and galvanic corrosion. This protective coating is effective in marine environments and aerospace applications where corrosion resistance is paramount. Cadmium compounds are also used as stable, vibrant pigments, creating shades of yellow, orange, and red for use in specialized paints, ceramics, and engineering plastics.
Health Risks and Environmental Fate
Despite its utility, Cadmium is classified as a toxic heavy metal and a known human carcinogen. The primary routes of exposure for the general public include smoking and the consumption of contaminated food and water. Cadmium is readily absorbed by crops, such as grains and vegetables, from contaminated soil, allowing it to enter the food chain.
Once absorbed by the body, Cadmium is stored for decades, accumulating in the kidneys, liver, and bones. Chronic exposure can lead to severe health issues, including kidney dysfunction and weakened bones due to disrupted calcium metabolism. Itai-Itai disease, a painful bone and kidney disorder, is linked to environmental contamination. Because Cadmium is environmentally persistent and can travel long distances, regulatory efforts focus on minimizing its use in consumer products and controlling emissions from mining and waste disposal.