Tin (II) oxide structure, properties, nomenclature, uses

The tin (II) oxide is a crystalline inorganic solid that is formed by oxidation of tin (Sn) by oxygen, where tin acquires a 2+ valence. Its chemical formula is SnO. Two different forms of this compound are known: black and red. The common and most stable form at room temperature is the black or bluish-black modification..

This form is prepared by hydrolysis of tin (II) chloride (SnCl_two) in aqueous solution, to which is added ammonium hydroxide (NH₄OH) to obtain a hydrated oxide precipitate of Sn (II) whose formula is SnO.xH_twoOr, where x<1 (x menor que 1).

The hydrated oxide is a white amorphous solid, which is then heated in suspension at 60-70 ºC for several hours in the presence of NH₄OH, until obtaining the pure black crystalline SnO.

The red form of SnO is metastable. It can be prepared by adding phosphoric acid (H₃PO₄) - with 22% phosphorous acid, H₃PO₃ - and then NH₄OH to a SnCl solution_two. The white solid obtained is heated in the same solution at 90-100 ° C for about 10 minutes. In this way the pure red crystalline SnO is obtained.

Tin (II) oxide is a starting material for the production of other tin (II) compounds. For this reason, it is one of the tin compounds that has appreciable commercial importance..

Tin (II) oxide has low toxicity as occurs with most inorganic tin compounds. This is due to its poor absorption and rapid excretion from the tissues of living beings..

It has one of the highest tolerances of tin compounds in tests on rats. However, it can be harmful if inhaled in large amounts..

Article index

• 1 Structure
  • 1.1 Blue-black tin (II) oxide
  • 1.2 Tin (II) oxide red
• 2 Nomenclature
• 3 Properties
  • 3.1 Physical state
  • 3.2 Molecular weight
  • 3.3 Melting point
  • 3.4 Density
  • 3.5 Solubility
  • 3.6 Other properties
• 4 Uses
  • 4.1 In the production of other tin (II) compounds
  • 4.2 In jewelry
  • 4.3 Other uses
  • 4.4 Recent innovations
• 5 References

Structure

Blue-black tin (II) oxide

This modification crystallizes with a tetragonal structure. It has an arrangement of layers in which each Sn atom is at the top of a square pyramid, the base of which is formed by the 4 closest oxygen atoms..

Other researchers claim that each Sn atom is surrounded by 5 oxygen atoms that are located roughly at the vertices of an octahedron, where the sixth vertex is presumably occupied by a pair of free or unpaired electrons. This is known as the Φ-octahedral arrangement.

Tin (II) oxide red

This form of tin (II) oxide crystallizes with an orthorhombic structure.

Nomenclature

- Tin (II) oxide

- Stannous oxide

- Tin monoxide

- Stannous oxide

Properties

Physical state

Crystalline solid.

Molecular weight

134.71 g / mol.

Melting point

1080 ºC. It decomposes.

Density

6.45 g / cm³

Solubility

Insoluble in hot or cold water. Insoluble in methanol, but dissolves quickly in concentrated acids and alkalis.

Other properties

If heated to more than 300 ºC in the presence of air, tin (II) oxide rapidly oxidizes to tin (IV) oxide, presenting incandescence.

It has been reported that under non-oxidizing conditions, the heating of tin (II) oxide has different results depending on the degree of purity of the starting oxide. Generally disproportionate into metallic Sn and tin (IV) oxide, SnO_two, with various intermediate species that eventually become SnO_two.

Tin (II) oxide is amphoteric, as it dissolves in acids to give Sn ions^two+ or anion complexes, and also dissolves in alkalis to form solutions of hydroxy-tinnate ions, Sn (OH)₃^-, which have a pyramidal structure.

In addition, SnO is a reducing agent and reacts rapidly with organic and mineral acids..

It has a low toxicity when compared to other tin salts. Its LD50 (50% lethal dose or median lethal dose) in rats is more than 10,000 mg / kg. This means that more than 10 grams per kilogram is required to kill 50% of the rat specimens under a given test period. In comparison, stannous (II) fluoride has an LD50 of 188 mg / Kg in rats..

However, if inhaled for a long time, it is deposited in the lungs because it is not absorbed and can cause stanosis (infiltration of SnO dust into the lung interstices).

Applications

In the production of other tin (II) compounds

Its rapid reaction with acids is the basis of its most important use, which is as an intermediate in the manufacture of other tin compounds..

It is used in the production of tin (II) bromide (SnBr_two), tin (II) cyanide (Sn (CN)_two) and tin (II) fluoroborate hydrate (Sn (BF₄)_two), among other tin (II) compounds.

Tin (II) fluoroborate is prepared by dissolving SnO in fluoroboric acid and is used for tin and tin-lead coatings, especially in the deposition of tin-lead alloys for soldering in the electronics industry. This is due, among other things, to its high coverage capacity.

Tin (II) oxide is also used in the preparation of tin (II) sulfate (SnSO₄), through the reaction of SnO and sulfuric acid, H_twoSW₄.

The SnSO₄ obtained is used in the tinning process for the production of printed circuit boards, for the finishing of electrical contacts and for the tinning of kitchen utensils.

The hydrated form of SnO, the hydrated tin (II) oxide SnO.xH_twoOr, it is treated with hydrofluoric acid to obtain stannous (II) fluoride, SnF_two, which is added to toothpastes as an agent to fight cavities.

In jewelry

Tin (II) oxide is used in the preparation of gold-tin and copper-tin ruby ​​crystals. Apparently its function in this application is to act as a reducing agent.

Other uses

It has been used in photovoltaic devices for the production of electricity from light, such as solar cells.

Recent innovations

Arranged SnO nanoparticles have been used in carbon nanotube electrodes for lithium-sulfur batteries.

SnO-prepared electrodes exhibit high conductivity and little volume change in repetitive charge and discharge cycles.

In addition, SnO facilitates rapid ion / electron transfer during oxidation-reduction reactions that occur in such battery systems..

References

1. Cotton, F. Albert and Wilkinson, Geoffrey. (1980). Advanced Inorganic Chemistry. Fourth Edition. John Wiley & Sons.
2. Bailar, J.C .; Emeléus, H.J .; Sir Ronald Nyholm and Trotman-Dickenson, A.F. (1973). Comprehensive Inorganic Chemistry. Volume 2. Pergamon Press.
3. Ullmann's Encyclopedia of Industrial Chemistry. (1990). Fifth Edition. Volume A27. VCH Verlagsgesellschaft mbH.
4. Kirk-Othmer (1994). Encyclopedia of Chemical Technology. Volume 24. Fourth Edition. John Wiley & Sons.
5. Ostrakhovitch, Elena A. and Cherian, M. George. (2007). Tin. In Handbook of the Toxicology of Metals. Third Edition. Recovered from sciencedirect.com.
6. Kwestroo, W. and Vromans, P.H.G.M. (1967). Preparation of Three Modifications of Pure Tin (II) Oxide. J. Inorg. Nucl. Chem., 1967, Vol. 29, pp. 2187-2190.
7. Fouad, S.S et al. (1992). Optical properties of stannous oxide thin films. Czechoslovak Journal of Physics. February 1992, Volume 42, Issue 2. Recovered from springer.com.
8. A-Young Kim et al. (2017). Ordered SnO nanoparticles in MWCNT as a functional host material for high-rate lithium-sulfur battery cathode. Nano Research 2017, 10 (6). Recovered from springer.com.
9. National Library of Medicine. (2019). Stannous oxide. Recovered from: pubchem.ncbi.nlm.nih.gov