504
ELEMENTS OE MATERIA MEDICA.
afterwards smelted with Welsh culm and limestone, by which blocktin is procured; the finest kind of which is called refined tin (Mr. JohnTaylor, Ann. Phil. iii. 449).
Besides the two varieties of tin just described, other kinds are metwith in commerce. Malacca tin occurs in quadrangular pyramids, withflattened bases. Banca tin is met with in wedge-shaped pieces.
Properties. — In its massive form it is a yellowish-white metal,having a peculiar odour when rubbed or handled. Its sp. gr. is 7'29.It melts at 442° F. and at a white heat is volatilized. It is malleable,and forms sheet tin and tin foil (stannum foliatum), but is sparingly duc-tile. Its equivalent is 58.
Tin may be reduced to powder, by pouring melted tin into an ironmortar, and rubbing until it is cold ; or by shaking melted tin in awooden box, the inside of which has been rubbed with chalk. In thisstate it constitutes powdered or granulated tin (pulvis stanni, Ph . Dub.,Ed. and U. S.) This as well as tin filings (stanni limatura, Ph . Ed. seurasura stanni) have been used in medicine.
Characteristics. —Boiled in strong hydrochloric acid, we obtain asolution of protocliloride of tin, which possesses the following charac-ters :—Potash causes a white precipitate, soluble in excess of the pre-cipitant ; hydrosulphuric acid, a brown ; and chloride of gold, a purpleprecipitate (the purple powder of Cassius). If protochloride of tin beheated with nitric acid, we obtain a perchlori.de which causes a yellowishprecipitate with hydrosulphuric acid.
Physiological Effects. —In the mass, tin has no operation on thebody, except that arising from its form and weight. Powdered tin is notknown to produce any disorder in the functions of the body. It appears,however, that acid, fatty, saline, and even albuminous substances, mayoccasion colic and vomiting by having remained for some time in tinvessels. Oxide of tin is poisonous, according to Orfila ( Toxicol. Gen.)-,but Schubarth (quoted by Dr. Christison, Treat, on Poisons) found itinactive.
Uses. —Powdered tin has been employed with great success byvarious eminent practitioners, as a vermifuge, particularly in tape-worm.Dr. Alston (Med. Essays, v. 89, 92 ; also Led. on Mat. Med. i. 150) ex-plains its operation on mechanical principles : he supposes that the powderof tin gets betwixt the worms and the inner coat of the alimentary canal,and causes them to quit their hold, so that purgatives easily carry themaway with the faces. It has, however, been asserted that water in whichtin has been boiled is anthelmintic, at least so says Pitcairn and Pietsch(quoted by Richter, Ausf Arzneim. iv. 553); wine which has beendigested in a tin vessel is also said to be noxious to worms. . If thesestatements be true, the before-mentioned mechanical explanation isinadmissible. Some have, therefore, supposed that the efficacy mustdepend on the tin becoming oxidized in the alimentary canal; othershave fancied that arsenic, which is frequently found in tin, is the activeagent; while, lastly, some have imagined that the metal, by its action onthe fluids of the canal, generated hydrogen, or hydrosulphuric acid, whichdestroyed these parasites.
Dr. D. Monro (Treat, on Med. and Pharrn. Chem. i. 289), Fothergill,and Richter, have used powdered tin in epilepsy produced by worms, and,as it is stated, with advantage.