Page:The American Cyclopædia (1879) Volume XVI.djvu/846

 816 ZINO in procuring for him the offices of aulic coun- cillor and physician to the court of Hanover, to which place he removed in 1768. Excessive employment here brought on an internal dis- order requiring a visit to Berlin for an opera- tion in 1771, during which he made the ac- quaintance of Frederick the Great. After a few months he was restored to health, but domestic afflictions plunged him into a fit of unusual despondency. After a second mar- riage he succeeded in throwing off in a mea- sure his habitual gloom. He now published his completed work " On Solitude " (4 vols., Leip- sic, 1784-'5), which obtained an immense pop- ularity throughout* Europe, and is the most matured of all his productions, and that with which his name is now most commonly asso- ciated. Zimmermann attended Frederick the Great during his last illness at Berlin in 1786, and published Ueber Friedrich den Orossen und meine Unterredung mit Him kurz vor seinem Tode (Leipsic, 1788), and Fragmente uber Friedrich den Grossen (3 vols., 1790 et seq. ; English trans- lation, " Select Views of the Life, Reign, and Character of Frederick the Great," by Major Neumann, 2 vols., 1792). These works in- volved him in bitter controversies with public men whose characters he had assailed, and were in general so full of coarse calumny and mendacity as to render it certain that he was entering a more dangerous phase of hypochon- driasis, under the influence of which the po- litical movements of the times seemed to him only conspiracies against religion and social order. The French revolution and the ideas propagated by it inspired him with a sort of frenzy ; and for the purpose of arresting the republicanism which seemed likely to subvert all existing institutions, he addressed a memoir to the emperor Leopold II., recommending a league of the absolute governments against all revolutionists. In 1794 he was compelled by physical and mental exhaustion to give up all his occupations. See Zimmermann 1 s Kran- kengeschichte, by Wichmann (Hanover, 1796), and Vie de Zimmermann, by 8. A. Tissot (Lausanne, 1797; English translation, London, 1797). His autobiography appeared at Hano- ver in 1791. ZINC, or Spelter (symbol, Zn ; chemical equi- valent, 65 ; specific gravity, 7'03 to 7'2), a highly lustrous white metal, with a bluish gray tint. It crystallizes in forms not perfectly re- cognized according to Noggerath and Plattner in hexagonal prisms, and according to G. Rose in monometric forms also, hence probably di- morphous. On fresh fractures it presents a beautiful foliated crystalline structure. It is comparatively soft, but harder than tin, and is brittle or malleable and ductile, according to temperature, viz. : at ordinary temperatures brittle, parting along cleavage faces ; between 100 and 150 0. (212 and 302 F.) malleable and ductile, so that it can be drawn into wire or beaten or rolled into plates ; at 200 0. (392 F.) so brittle that it may be pulverized in a mortar having this temperature. It is fusible at 412 0. (773 F.), and volatile at high red heat. It expands rapidly when heated (^fj- of its length in passing from to 100 C.), and contracts when cooled. The boiling point, according to Deville, is about 1040 C. (1904 F.) ; according to Becquerel, 891 0. (1636 F.). The temperature of melting also affects the brittleness. Cast at a high heat, zinc is brittle ; but cast at the lowest practicable tem- perature, it is malleable. The cause of this appears to lie in the connection between crys- talline structure and brittleness. In preparing zinc to be rolled, it is usually melted in large kettles, and before casting in warmed moulds pieces of solid zinc are thrown into the bath to reduce its temperature. The process of rolling hardens it, but it may be annealed at low heat. It is not highly tenacious ; zinc wire -fa in. in diameter sustains 25 Ibs., or about two tons per square inch of section. The vapor of zinc burns in the air with a bril- liant bluish white flame to flocculent white oxide (zinc white, the nihil album, flores zinci, or lana philosophica, of the alchemists, and the pompholyx of the ancient Roman metallur- gists), which is not easily fusible or volatile, but is mechanically carried by the draft at- tending combustion, so that its deposition in settling chambers as an almost impalpable pre- cipitate has a superficial resemblance to sub- limation and condensation. If zinc is melted and brought to glowing heat under access of air, it burns to oxide, which may be skimmed from the metallic bath. Fine turnings of zinc will burn to oxide if lighted with a match. Exposed to a moist atmosphere, the metal soon loses its lustre, acquiring a thin gray film (often called oxide, and sometimes suboxide, but more correctly a basic carbonate), which, close- ly adhering to it, protects it from further change. The usefulness of this property is evident. Pettenkofer found- that upon a sheet of zinc which had been exposed as part of a roof for 27 years, the oxidizing action had penetrated but 0*01 millimetre. In the pres- ence of air, zinc decomposes water, producing zincic oxide and liberating hydrogen. In this way hydrogen is made for laboratories, dilute sulphuric or hydrochloric acid being used in- stead of pure water, and zincic sulphate or chloride being formed, which is removed by solution from the surface of the metal, greatly assisting the rapidity and uniformity of the liberation of hydrogen. Boiling solutions of potash are also decomposed by zinc in a simi- lar manner, the resulting zincic oxide being dissolved. Zinc is the most electro-positive of the metals, whence its use in galvanic batteries, &c. ; and the presence of electro-negative met- als, producing galvanic action, facilitates the reactions above described. Indeed, chemically pure zinc is with difficulty acted upon by acids in a glass vessel. The ordinary zinc of com- merce is never perfectly pure, but contains various ingredients derived from its ores or