Lead(II) thiocyanate is a compound, more precisely a

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

, with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

Pb(SCN)₂. It is a white crystalline solid, but will turn yellow upon exposure to light. It is slightly soluble in water and can be converted to a basic salt (Pb(CNS)₂·Pb(OH)₂ when boiled. Salt crystals may form upon cooling. Lead thiocyanate can cause

lead poisoning Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by lead in the body. Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, infertility, numbness and paresthesia, t ...

if ingested and can adversely react with many substances. It has use in small explosives, matches, and dyeing. Lead(II) thiocyanate is reasonably soluble at room temperature, thus it may be difficult to identify in a solution with low

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number concentration'', ...

of lead(II) thiocyanate. Although it has not been confirmed by other sources than the author of this article, experiments show that even if there is no precipitation of lead(II) thiocyanate in the solution, crystals of the salt may form.

Synthesis

Lead(II) thiocyanate can be formed from the acidification of lead(II) nitrate, Pb(NO₃)₂, with nitric acid, HNO₃, in the presence of

thiocyanic acid Thiocyanic acid is a chemical compound with the formula and structure , which exists as a tautomer with isothiocyanic acid (). The isothiocyanic acid tautomer tends to dominate with the compound being about 95% isothiocyanic acid in the vapor ...

, HSCN. It may also be made by reacting lead(II) acetate (Pb(CH₃COO)₂) solved in water with either

potassium thiocyanate Potassium thiocyanate is the chemical compound with the molecular formula KSCN. It is an important salt of the thiocyanate anion, one of the pseudohalides. The compound has a low melting point relative to most other inorganic salts. Uses Ch ...

(KSCN) or ammonium thiocyanate (NH₄SCN), thus causing a white

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

of solid lead(II) thiocyanate according to the ion reaction: :Pb²⁺(aq) + 2SCN⁻(aq) → Pb(SCN)₂(s) According to

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

, the anhydrous salt is a coordination polymer. The Pb²⁺ ions are each bonded to eight thiocyanate anions, with four Pb-S and four Pb-N bonds. The motif is reminiscent of the fluorite structure. Strontium thiocyanate, calcium thiocyanate, and barium thiocyanate adopt the same structure.

Reactivity

When exposed to UV or visible light, lead thiocyanate will turn yellow due to the presence of sulfur. It is violently oxidized by nitric acid and will release highly toxic

hydrogen cyanide Hydrogen cyanide (formerly known as prussic acid) is a chemical compound with the chemical formula, formula HCN and structural formula . It is a highly toxic and flammable liquid that boiling, boils slightly above room temperature, at . HCN is ...

gas on contact with acid. At high temperatures it releases

sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...

gas. Like other metal cyanides, it explodes on heating when mixed with

sodium nitrate Sodium nitrate is the chemical compound with the chemical formula, formula . This alkali metal nitrate salt (chemistry), salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordi ...

Health hazards

Skin and eye irritant, can induce

by ingestion or inhalation. Symptoms include gastrointestinal disorders, irritation of digestive tract, leg cramps, muscle weakness,

paresthesia Paresthesia is a sensation of the skin that may feel like numbness (''hypoesthesia''), tingling, pricking, chilling, or burning. It can be temporary or Chronic condition, chronic and has many possible underlying causes. Paresthesia is usually p ...

. High doses can result in coma or death. Symptoms present in 1 to 2 days.

Lead poisoning

Most lead(II) salts have a sweet taste making them a hazard for continued consumption small children. While lead thiocyanate was likely not used in paints due to its light sensitivity, many lead based paints have been used pre-1970s. The paint has a tendency to peel and fall off making it likely to expose small children and pets. Since lead poisoning occurs with the binding of lead(II) to biological systems, research has been done to find ligands that more preferentially bind to lead(II) than other biological targets in an effort to combat the effects of lead poisoning.

Uses

Lead thiocyanate is used in explosives, specifically an ingredient in primers for small-arms cartridges, safety matches, and to reverse aniline black dyeing (Gideon). It can also be used as a precursor for preparing perovskite solar cells.

References

External links

Source for other names and health hazards
{{Lead compounds Thiocyanates Lead(II) compounds