Arsenic and Old Myths Mickey Sarquis Miami University-Middletown Middletown. OH 45042 Alchemical Symbols
Arsenic in History
Anxiety toward arsenic is not difficult to understand. Arsenic compounds have long been a preferred agent of homicide and suicide. Arsenic trioxTde, for example, a&ounted for ap"white arsenic" "red orrenic" nroximatelv one third of the reported poisonine attempts in arsenic trioxide ~~ln(ls Fmnm in 188%The tmit charac~rrt ~ i a r . ; e ~ ~ i c c o m ~ rhas As& ;also heen stressed in nunscirntiiic literature. liv~selrit~g's drama, "Arsenic and Old Lace", is a prime example. ~ l t h o u g h synthesized in a deliberate attempt to exploit the antibacterial arsenic was only one of the poisons used by the Brewster siseffects of inorganic arsenicals while reducing their toxicity. ters, titles of "Strychnine and Old Lace"or "Cyanide and Old These organic arsenicals were ~rimarilvused aeainst s l e e ~ i n a Lace" would not have carried nearly the same dramatic imsickness:'syphilis, and relate2 parasitic diseases. w i t h the pact. advent of penicillin. however. the maioritv " .of these have fallen Napoleon Bonaparte may have been a victim of arsenic into disuse. poisoning during his exile on St. Helena. Neutron activation Structure of Arsphenamine (Salvarsan) analysis of hair reportedly taken from Napoleon's head showed arsenic concentrations considerably higher than normal. Descriptions of Napoleon's symptoms during his later venrs has led some researchers to conclude that he intermittently suffered from chronic and acute arsenic poisoning. Dehate exists as to whether this was a result of some homicidal plot or a honest medicinal treatment. Arsenic compounds (often referred to as arsenicals) have been used as medicines and tonics since recorded history. Properties of Arsenic Ancient Chinese alchemists prepared elixirs of "The Three Metallic arsenic is a brittle.. erav Yellows"-orpiment (arsenic trisulfide, AsSd, realgar (te" . solid. which when freshlv cut has a bright metallic luster. It rapid& tarnishes when eitraarsenic tetrasulfide, As&), and gold. There are some reposed to air forming a black modification of arsenic trioxide. Arsenic has two other nonmetallic allotropic forms. The yellow form is obtained by rapid cooling of arsenic vapor. Yellow arsenic is converted to the gray modification upon short exposure to ultraviolet lirht. Arsenic has four oxidation states, -3, 0, +3, and +5. &sine (H:lAs) and methylarsines are characteristic of the -3 oxidation state. They are generally unstable in air. Arsenic metal is usually formed by the reduction of arsenic trioxide with carbon and sublimation in an inert atmosphere of nitrogen gas. ~
Ar06(s)
ports that indicate that sulfur, rather than cold, was the third compunmt. These mixtures were prescrihed for various imhalances in a,ul, health, nnd discip.ine. Il~ppucratea146(1 B.C.) reportedly recommended apaste of arsenic sulfides as treatment for ulcers. Medicinal uses of arsenic apparently reached their peak in the eighteenth and nineteenth centuries. Fowler's solution, a mixture of arsenic trioxide, potassium bicarbonate, alcohol, and water, was one of the principle therapeutic drugs of this time. It was prescribed for symptomatic relief from such afflictions as epilepsy, asthma, psoriasis, and eczema. Mountaineers in the Stvrian Alps of Austria consumed certain arsenic compounds on a regular basis in amounts exceedine s u.. p ~ o s e dtoxic levels. These arsenicals reportedly increased ones physical strength, stamina, and appetite, and produced clear complexions. The origins of this custom are difficult to trace, hut the practice of "arsenic eating" was sited hy Schroeder and Balassa as recently as 35 years ago. The biochemistry of this supposed tolerance to arsenic is unfortunately not understood. Ehrlich's development of Salvarsan (arsphenamine) in the early part of this century, was a milestone in chemotherapy. It was the first of over 32,000 organic arsenicals that were
+ 6C (s)
-
Asd(g)
+ 6CO (g)
In AsaOe. arsenic has the +3 oxidation state. (This compound is comm&dy called arsenic trioxide which correspondi to its empirical formula rather than its molecular formula.) As406 is by-product of the smelting of nonferrous ores. It can be catalytically or microbially oxidized to the +5 oxidation state as AsOs (arsenic pentoxide) or HaAsOd (arsenic acid). Arsines (As -3) and arsenites (As +3) are in general more toxic than arsenates (As +5). Arsenic may act as a metal, forming oxides and chlorides, or as a nonmetal, forming acids. When heated in air, elemental arsenic hurns with a bluish flame and produces dense white fumes of arsenic trioxide. Arsenic is insoluble in water and d
