Cadmium (Cd) is one of the transition metals that are located in the d-block of the periodic table. Cadmium is located in the fifth period and twelfth group of the periodic table. Cd possesses an atomic number of 48 and an atomic mass of 112.411g. It was first discovered by the German scientist, Friedrich Strohmeyer in 1817 in Germany. At that time, cadmium was commonly used to protect iron and steel from corrosion as it was inserted as a sacrificial anode. Additionally, it was used in the manufacture of nickel-cadmium batteries. Cadmium is a highly toxic element so it has to be handled with great caution.
Abundance of Cadmium in Nature: Cadmium cannot be easily found in its elemental form naturally. It has been detected in the Earth's Crust in very minute amounts that do not exceed 0.1 to 0.2 ppm. However, it usually occurs in the form of compounds accompanied with other elements. The most common naturally occurring compounds of cadmium include cadmium sulfide, cadmium carbonate, carbon oxide, etc. Carbon sulfide, commonly known as the mineral Greenockite, is considered a common source of cadmium. Most of the extracted pure cadmium are obtained as products of the zinc refinement process.
Properties and Uses of Cadmium: Cadmium is a silvery grey and soft malleable metal especially when it is abundant in its pure form. It is widely used as a corrosion resistant during steel and iron electroplating. Due to their brilliant colors, cadmium containing compounds have also been used in oil paints such as cadmium yellow. Cadmium is also used as an electricity conductor. Like zinc and tin, cadmium metal cries when it is bent rapidly i.e. emits a high pitched sound.
Cadmium Salts: Cadmium sulfate refers to a series of hydrated forms of cadmium sulfate salts with the chemical formula of CdSO4·xH2O, where x represents the number of water molecules. All of them are white crystalline salts that are highly soluble in water. The most common of them is the monohydrate form that possesses a chemical formula of CdSO4·H2O. Then come the next two commons salts that possess the chemical formulas of CdSO4·8⁄3H2O and the anhydrous salt (CdSO4).
Preparation of Cadmium Sulfate: Cadmium sulfate can be prepared through the reaction of cadmium metal, cadmium oxide or cadmium hydroxide dilute sulfuric acid as shown in the following reactions:
Cd + H2SO4 → CdSO4 + H2
CdO + H2SO4 → CdSO4 + H2O
Cd(OH)2 + H2SO4 → CdSO4 + 2 H2O
Properties and Uses of Cadmium Sulfate:
- Cadmium sulfate is a white crystalline salt that possesses the chemical formula of CdSO4.xH2O when it is hydrated, while CdSO4 when it is dehydrated.
- When used in high amounts, cadmium sulfate can cause throat dryness, cough, chest constrictions and headache.
- Cadmium sulfate is used as a pigment in fluorescein screens.
- Cadmium sulfate has some medicinal properties. For example, it is used as an antiseptic. In addition, it is used in the treatment of venereal diseases and rheumatism.
- Cadmium sulfate has been used as an indicator for the presence of hydrogen sulfide gas.
