Tin

TIN, Stannum (Sn), belongs to the group of heavy metals; atomic weight 118.7. It is extracted from tin stone (tin oxide, SnO₂), which is common in the East Indies, Australia, South Africa, and Peru. Tin is a shiny, silvery-white metal with a bluish tint; it is distinguished by its softness, flexibility, and malleability. It has a crystalline structure, which appears particularly clearly when treated with hydrochloric acid. Specific gravity 7.29; melting point 231.7°. It can easily be rolled into thin sheets (foil, stanniol). In air, tin retains its metallic luster; in a molten state, upon contact with air, it oxidizes on the surface into tin dioxide. It dissolves in HCl and slowly in warm dilute sulfuric acid with the formation of hydrogen. In concentrated sulfuric acid, tin dissolves upon heating, turning into tin sulfate, SnSO₄, with the formation of sulfur dioxide. In an excess of aqua regia, tin turns into tin tetrachloride, SnCl₄; in cold dilute nitric acid, into tin nitrate, Sn(NO₃)₂, without the formation of hydrogen; in hot concentrated nitric acid, into insoluble metastannic acid hydrate, H₂SnO₃; in concentrated potassium alkali, into the potassium salt of metastannic acid, K₂SnO₃, with the evolution of hydrogen. In its compounds, tin can be divalent and tetravalent. Tin was used against epilepsy. In ancient times, tin in powder form was used as an anthelmintic agent. Recently, it has begun to be recommended as an internal antiseptic in the treatment of furunculosis. According to Chome and Pronin (1919), tin perchlorate in 0.3–0.5% solutions possesses a specific effect on staphylococci; therefore, it is used for abscesses, lymphangitis, etc. For furunculosis and other dermatitides, 1–2 g (several times a day) of metallic tin powder or tin oxide is given orally. When administering tin per os, it can be considered that it also acts directly on the digestive tract, irritating its walls and stimulating the intestinal musculature to increased peristalsis. Cases of tin poisoning are rare, as this metal does not easily pass into a soluble form and apparently does not possess a cumulative effect. There is almost no data regarding cases of acute poisoning in humans. After the introduction of soluble tin compounds into the blood, phenomena from the central nervous system (its excitation followed by paralysis) and cardiac arrest are observed. In chronic poisoning, gastroenteritis, ataxia, and motor paralysis are observed, which resembles chronic lead poisoning (Sollman). Salzer (1918) described a case of chronic poisoning resulting from the presence of a Watt metal plate in the mouth. In this case, phenomena from the central nervous system and anemia were observed. In the frog, tin salts paralyze the central nervous system, and later the heart. In mammals, diarrhea, colic, vomiting, general weakness were observed, as well as paralysis of some parts of the central nervous system and excitation of others, resulting in the development of ataxia, stiffness of movement, and sometimes convulsions, which in dogs are often preceded by twitching of individual muscle groups. The paralyzing effect on the central nervous system apparently extends primarily to the spinal cord. The amount of urine in experiments with animals turned out to be reduced; the urine contained protein and bladder epithelium. A possible source of tin poisoning is canned food packed in tin cans. Tin dissolves differently in various organic acids: poorly in acetic, better in malic, and even better in tartaric. In canned fish, amines formed therein facilitate the dissolution of tin. The tin content in certain types of canned food can reach several hundred mg per 1 kg of weight. It is possible that in some cases of consuming old, predominantly fruit, canned goods, phenomena of acute but mild poisoning may indeed be observed. Usually, however, tin is contained in canned food in such insignificant quantities that it can hardly be considered a possible source of poisoning. In any acute phenomena after consuming canned food, the assumption of the poor quality of the canned food itself is more probable. Of course, one should strive for such packaging of canned food that would not require introducing even the most insignificant amounts of tin into the body. Among tin preparations, the following can be noted: 1) Stannum foliatum (zinc foil, stanniol)—tin rolled into thin sheets. Used for packaging various products, e.g., chocolate, cheese, tobacco. It often contains more than 1% lead. For packaging pharmaceutical products, e.g., suppositories, only the purest grades of Stannum foliatum should be used, containing at most only traces of lead. 2) Stannum praecipitatum—a gray loose powder. Dissolves in hydrochloric acid with the evolution of hydrogen. Used externally for corneal opacities. 3) Boli Stanni compositi (Cort. Granati radic. plv. 10.0, Cort. Cinnamomi plv., Stanni pulverati aa 5.0, Sirupi simplicis q. s. f. Boli 10). A remedy against tapeworms; 1 pill every 1–2 hours. 4) Stannosan—tablets containing metallic tin. Used for furunculosis and pyodermas. 5) Stannum chloratum (tin chloride) crystallisatum, SnCl₂ + 2H₂O, colorless crystals, usually having a moist appearance, distinguished by an acidic reaction. In water acidified with hydrochloric acid, as well as in alcohol, tin chloride dissolves almost to complete transparency of the solution; in a large amount of water, it decomposes, with basic tin chloride, Sn(OH)Cl, precipitating. Tin chloride captures oxygen from the air and turns into insoluble basic tin dichloride, SnOCl₂. In the past, tin chloride was given in the form of pills or solution at 0.005–0.01–0.03 several times a day for epilepsy and some neuroses and for tapeworms. Externally, it is used in a 0.1–0.2% solution against eczema.