Classification of microbes based on specific nutritional requirements. Heterotroph = use carbon sources (sugars, alcohols, carbs, fats, proteins) Autotroph = use inorganic carbon source (CO2) Chemotroph = use organic (glucose)/inorganic (reduced Fe2+) chemicals for energy.
You can color any metal containing iron, such as steel, with the oven heat of an ordinary kitchen range. Depending on the temperature setting, the steel changes color across a spectrum of shades ranging from pale yellow to dark blue. In addition, literally hundreds of chemicals will change the color of metal surfaces. Some of them are too toxic for amateurs to use. For example, cyanides, nitric acid, chromic acid, mercuric chloride, and lead acetate are hazardous chemicals only professionals should attempt to use.
The first thing most people think of when they hear the word cobalt is the color blue. While the purified metal is a grey steel color, the salts that include cobalt atoms are many shades of blue. The element has been used for hundreds of years, but was named in 1735 by a chemist named Brandt. We often mention that you cannot find this element or that element free in nature.