Element Antimony, Sb, Metalloid

With antimony we commence the consideration of the metals of the tin group, in which a number of elements are classed together belonging to different natural families and forming corresponding sub-groups. Their common characteristic is the predominating tendency to form acid compounds in place of the basic ones yielded by the other metals. Their oxides, especially those comparatively rich in oxygen, behave as the anhydrides of acids, and their sulphur compounds dissolve in the solutions of the alkali sulphides with formation of thio-salts (vide infra). The last characteristic which is of importance in analytical chemistry has given rise to the formation of the whole group, and the relations which are here met with will be presently discussed in greater detail.

On account of the manifold and widely extending affinity relations existing between the elements, we shall repeatedly find resemblances to other groups, and it would be possible to class several of the elements considered here along with others previously discussed. By reason, however, of the variety of the relationships, a system of the elements, sufficient in all respects, cannot be framed, and the arrangement which has here been retained has therefore been determined chiefly by didactic considerations.

Antimony is allied on the one hand to bismuth, and on the other, to arsenic and phosphorus. It therefore forms a transition element between the metals and the non-metals, but is still essentially on the side of the metals. Its combining weight is Sb = 120.2.

Antimony is a grey-white, lustrous metal, having the density 6.7; from the fused mass it solidifies in a distinctly crystalline form, and is at all temperatures so brittle that it can be easily ground or pounded to a powder. It melts at a red-heat, and volatilises at a high temperature. The vapour exhibits a variable molar weight in the neighbourhood of 290. This number corresponds to no simple formula, but lies between Sb₂ and Sb₃; probably, therefore, we are dealing with a mixture of different kinds of vapour, perhaps Sb₄ and Sb.

In the potential series antimony stands beside bismuth; it does not, therefore, decompose dilute acids, and it also remains unchanged in the air. On being heated it readily oxidises; a piece of antimony fused on charcoal before the blowpipe, continues to glow even after the flame has been removed, the antimony burning to antimony oxide. If a small globe of strongly heated antimony is thrown on a piece of paper with upturned edges, it skips about on this, burning all the while, and leaves very regularly marked, hyperbolic trails.

Besides the ordinary antimony, an allotropic form of less stability is known, which is obtained as a silver-white metal, of density 5.78, by slowly decomposing a concentrated solution of antimony chloride in hydrochloric acid with the electric current. The metal which is deposited falls to a powder with slight explosion on being scratched by a sharp body, ordinary grey antimony being formed with considerable evolution of heat. This allotropic metal is not pure, but contains antimony chloride, the amount of which varies with the conditions of the experiment.

Antimony is known from high antiquity. Oriental countries were familiar with Antimony houseware at least as early as 3000 BC. In ancient Egypt in 19^th century BC antimonite powder (natural Sb₂S₃) called mesten or stem was used for eyebrows blacking. In ancient Greek it was known as as stimi and stibi, from which Latin stibium derived. This element is called antimonium since 12-14 centuries BC. In 1789 Lavoisier put Antimony into the chemical elements list under the name antimoine related to English antimony. Spanish and Italian antimonio, German Antimon. Russian "surma" appears from Turkish powder surme, lead glance PbS, also used for eyebrows blacking (alternative interpretation: comes from Persian word "surma" which means "metal"). 15^th century German alchemist Basilius Valentinus, also known as Basil Valentine, gave detailed description of antimony's properties and extraction methods.

Early History

There can be little doubt that antimony was known in ancient times, either in the form of the metal or in compounds. The Chinese were acquainted with the metal five thousand years ago; and certain references in the Old Testament (II Kings, 9, 30; Ezekiel, 23, 40; Jeremiah, 4, 30) have been considered by most commentators to refer to stibnite or sulphide of antimony.

The Macro-structure of Antimony.

Ancient bronzes discovered by archaeologists in many parts of the world have been found to contain antimony; a vase found by M. de Saizec at Tells in Chaldea consisted of almost pure antimony; and an Egyptian copper ewer and basin of the Fifth or Sixth Dynasty has been shown to be plated with antimony.

It has been suggested that the knowledge of antimony passed from the East through Arabia into Europe by the agency of the Arabic chemist Djaber or Geber, who lived in the eighth century. References to antimony in the literature of the Middle Ages are extremely confusing, however, and it is not until towards the end of the sixteenth century that the obscurity is dispersed. Robert Boyle was clearly familiar with the starred appearance of the cast metal, to which he refers as the starry regulus of Mars and antimony (see fig).

The confusion which exists with regard to the early history of antimony is to a great extent due to the ambiguity of the origin and meaning of the words antimonium and stibium. Both words appear to have been employed to indicate in some cases the metal, in others the sulphide mineral stibnite. In addition, the metal itself was regarded by some authorities as a semi-metal, by others as a mixture of metals.

In Arabic writings the mineral stibnite is referred to as kohl, a word which is still retained, with a very different meaning, in alcohol. This term alcohol is used for stibnite in some Latin writings, but is more frequently found in the Spanish. The more usual Latin term was stibium. The origin of the term antimonium is more difficult to trace. The fable that it arose from the accidental poisoning of some monks may be dismissed on linguistic grounds. The word was used by Basil Valentine; and as in the original copy of his work (which was written in German) it always appears in italics, it is probably of Latin origin. This view is supported by the fact that one of the earliest recorded instances of the use of the word is in the Latin writings of Geber, who wrote in the thirteenth century. (This author is not to be confused with the Arabic chemist with a similar name, who flourished in the eighth century.) The word stibium appears to have been more generally employed, although both words survived until the time of Lavoisier; both were used indiscriminately to describe the metal and stibnite. An account of the available knowledge of antimony up to the beginning of the seventeenth century is to be found in the works of Basil Valentine.

Antimony compounds were largely employed in medicinal preparations in the Middle Ages. Paracelsus was one of the first to use them, having made butter of antimony (antimony trichloride) by distilling corrosive sublimate with antimony sulphide. Treatment with water yielded mercurius vitce (an oxychloride) - a preparation that was popularised by the Veronese physician Algarotus or Algaroth, and hence became known as Powder of Algaroth. Sulphide of antimony was itself used considerably for a time, but was practically discontinued after considerable discussion by the medical profession. Tartar emetic, the most widely employed antimony compound, was also probably used in early times. In ancient times wine was permitted to stand overnight in antimony goblets, and was taken medicinally on the following day. This practice persisted up to the time of Boyle, but was then superseded by the introduction of metallic pills of antimony.

Average crustal abundance of antimony is 5x10^-5 % by mass. Antimony is dispersed in magma and biosphere. It is concentrated in hydrothermal sources from hot underground waters. Antimony forms its own deposits as well as antimony-mercury, antimony-lead, gold-antimony, antimony-tungsten ones. Among 27 antimonial minerals stibnite, sometimes also called antimonite (Sb₂S₃) is the most important commercially. Due to its sulphur affinity antimony often forms an impurity in sulphides of such elements as arsenic, bismuth, nickel, lead, mercury, argentum and others elements.

Antimony's abundance per 100 g of dry matter is 0.006 mg, 0.02 mg in organisms of sea creatures and 0.0006 mg in terrestrial animals. Human and animals organisms are supplied with antimony through respiratory organs or digestive tract. It is extracted from organism by faces and, in insignificant amounts, with urine. Antimony's biological role remains unknown. It is separated in the thyroid liver and the spleen. Antimony is accumulated in erythrocytes mostly as Sb⁺³, in blood plasma. Antimony Maximum Permissible Concentration (MPC) is 10^-5 - 10^-7 g per 100 g of dry fabric. When MPC is exceeded antimony deactivates enzymes of lipid, carbohydrate and protein metabolism, perhaps as a result of sulfhydryl groups blocking.

The principal ores of antimony contain the mineral known variously as stibnite, antimonite or antimony glance, Sb₂S₃. Stibnite is found principally in France, Italy, Algeria and China, and to a smaller extent in Czechoslovakia, Spain, Portugal and Japan. In India, stibnite lodes in gneissose granite occur in the Punjab, and with cervantite in the Northern Shan states, while the tetrahedrite in Sleemanabad copper lodes is highly antimonial. The ores frequently contain gold, silver and arsenic, and are associated with galena, iron pyrites, spathic iron ore, quartz, calcite and barytes.

Other antimony minerals occasionally found in ores that are commercially valuable include cervantite or antimony ochre, Sb₂O₄, kermesite, 2Sb₂S₃.Sb₂O₃, valentinite, white antimony or antimony bloom, Sb₂O₃ (rhombic), and senarmontite, Sb₂O₃ (cubic).

Native antimony occurs in too small quantity to be commercially valuable.

Many other antimony minerals have been described. These are mainly complex sulphide minerals which may be regarded as thioantimonites or thioantimonates, oxidised minerals which may be antimonites or antimonates, and a few miscellaneous minerals difficult to classify. In the following list the formulae ascribed to the various minerals are intended to convey the approximate composition of the mineral; it is not suggested that they represent definite chemical compounds in all cases.

Antimony has also been found in animal tissues.