Page:The American Cyclopædia (1879) Volume XII.djvu/734

 720 OSKALOOSA OSMUNDA Brugsch (Eistoire tffigypte, 2d ed., 1875), finished existence, or the past. In the mytho- logical legends he is represented as the origi- nator of human civilization, and as engaged subsequently to his philanthropic services in a terrible contest with Typhon, or Evil (called in Egyptian Set or Sutekh). Typhon prevails ; Osiris is slain, and his dead body is fitted into a chest, thrown into the Nile, and swept out to sea. Isis, the consort of Osiris, learns of his death, and ransacks the world in search of his body. She finds it mutilated by Typhon. Then Osiris descends into the infernal regions, and has a later and different existence under the name of Serapis. Typhon is eventually slain by Horus, the son of Isis. Ancient writers say the Egyptians believed that the soul of Osiris entered the bull Apis, and it is assumed that the temple of Serapis mentioned by the Greeks was the temple of Osarapi, or Osiris Apis. On the judgment of Osiris and his assessors, in the "hall of double judgment" to which all the dead are led, depended the eternal fate of the soul. The "Book of the Dead" (see EGYPT, LANGUAGE AND LITERATUKE OF, vol. vi., p. 477) gives an account of the pilgrimage of the dead to Hades, where they are judged by Osiris. OSKALOOSA, a city and the capital of Mahas- ka co., Iowa, on the Keokuk and Des Moines Valley and the Central Iowa railroads, 55 m. E. S. E. of Des Moines ; pop. in 1870, 3,204 ; in 1875, 5,500, the city having been enlarged. It is situated on an elevation between the Des Moines and South Skunk rivers, and is well drained. It contains two planing mills, three founderies and machine shops, two flouring mills, two woollen factories, gas works, a grain elevator, a national and two private banks, and four hotels. There are three public school buildings, four weekly newspapers, and 12 churches. It is the seat of two colleges : Os- kaloosa college, established in 1861, under the control of the Disciples, and Penn college, founded in 1873, belonging to the Friends. The former in 1873-'4 had 5 instructors and 254 students, and the latter 5 instructors and 219 students. OSMAtf. See OTHMAN. OSMIUM, a metal belonging to the platinum group, discovered by Tennant in 1803 in pla- tinum ore, associated with iridium, ruthenium, and small quantities of rhodium, as an alloy called osmiridiura or iridosmine, and which forms the residue left after the treatment of platinum ore by aqua regia. The method for separating these different metals is that of Fremy, and depends upon the readiness with which osmium is oxidized and upon the vola- tility of the tetroxide produced. About 200 grammes of the platinum residue is roasted in a current of dry air in a porcelain or platinum tube heated to redness. Tetroxide of osmium or osmic acid is formed, and being volatile is passed into a series of glass flasks connected with the tube leading from the furnace, where it is condensed in beautiful needle-shaped crys- tals. The last flask contains a solution of caustic potash to absorb any tetroxide that may remain uncondensed, and an aspirator is at- tached to it to draw the air through the appa- ratus. The oxide is then by Berzelius's method digested with hydrochloric acid and mercury in a closed vessel at 284 F. Calomel is pro- duced by the decomposition of mercurous ox- ide which is formed by the union of the mer- cury with the oxygen of the osmic acid, and the osmium is left in a metallic state in the form of a black powder (OsO 4 + 8Hg+8Hcl =Os+4Hg a Cl a + 4H 9 O). The metal may also be obtained by digesting osmic acid with hy- drochloric acid and zinc. The properties of osmium vary with the mode of preparation. In the black pulverulent state its specific grav- ity is about 10, but when heated to the fusing point of rhodium it acquires a density of 21*4. At a still higher temperature, capable of melt- ing ruthenium and iridium and volatilizing platinum, osmium likewise volatilizes, but does not melt ; and it is in fact the most refractory of all metals. In a finely divided state it is highly combustible, and is easily oxidized by nitric or nitro-muriatic acid, in both cases be- ing converted into tetroxide. Five oxides of osmium are known, viz., OsO, Os 2 0s, OsOs, OsO 3, and Os0 4. The first three form salts with acids ; the fourth forms with a few bases salts called osmites. The tetroxide, often called os- mic acid, forms salts which are very unstable ; it can scarcely be regarded as a true acid, and its solution in water has no acid reaction with test paper. It is a powerful oxidizing agent, decolorizing indigo solution, and converting al- cohol into aldehyde and acetic acid. Its vapor is intensely pungent, irritates the mucous mem- brane, and is exceedingly poisonous. Accord- ing to Fremy, another oxide exists, OsOs, but it is very unstable. There are four chlorides, OsCl a, OsCl 3 , Os01 4 , and OsCle, called respec- tively dichloride, trichloride, tetrachloride, and hexachloride. Osmium burns in the vapor of sulphur, forming it is said fixed sulphides, anal- ogous to the oxides. All osmium compounds when heated with excess of nitric acid yield an unpleasant odor of tetroxide of osmium. OSMCNDA, a genus of ferns popularly known as flowering ferns. With one other genus they form the suborder Osmundacea, in which the spore cases are naked, globose, and each with a short pedicel or stalk ; their surface is cov- ered with a fine network, and they open into halves by a longitudinal slit. The name flow- ering fern is of course a misnomer, and was probably given on account of the showy char- acter of the fructification. They are the largest and most conspicuous of our native ferns, and are abundant in low grounds almost every- where, north and south, forming large clumps ; each rootstock throws up numerous fronds, which are often 5 ft. high. We have three species. The royal fern, 0. regalis, differs from the others in having twice-pinnate fronds, which bear the fructification at the top, where