OXALATES 463 



212: its vapour is irritating and deleterious, and has a peculiarly offensive odour, 

 hence the name of the metal from offfiri, an odour. Three combinations of osmium 

 and chlorine are known : protochloride, OsCl ; sesquichloride, Os 2 Cl s (this only 

 exists in solution) ; and bichloride, OsCl 8 (this exists only in a double salt, with 

 chloride of potassium, OsCP + KCl). Osmium combines also with phosphorus and 

 sulphur. 



OSAXXTJM-IRXDIUIMC, or Iridosmine. This alloy is found with platinum in 

 the province of Choco, in South America, and in the Ural Mountains. It was 

 first discovered by Mr. Smithson Tennant in the black scales which remain when 

 native platinum is dissolved in aqua regia. It is rather abundant with the alluvial 

 gold of California, occurring in small bright lead-coloured scales, sometimes six-sided 

 (Dana). It has been recently found in Gippsland, Victoria. 



The following analysis of this alloy is byBerzelius : Indium 46'77i osmium 49'35, 

 iron 0'74, rhodium 3-15. See IEIDIUST. 



OSMOSE FORCE. See EXOSMOSE and ENDOSMOSE. 



OSTEOCOLLA. The glue obtained from bones, by removing the earthy phos- 

 phates with muriatic acid, and dissolving the cartilaginous residuum in water, at a 

 temperature considerably above the boiling-point. 



OTTO, OTTAR, or ATTAR OF ROSES (from an Arabic word signifying 

 aroma), is a volatile oil, too well-known to require description as to its odour and 

 uses. It is obtained by distilling roses with water. It is manufactured exten- 

 sively at Ghazipoor in Hindostau, as well as at Shiraz in Persia. Polier says 

 that, to obtain a little less than 3 drachms of otto from 100 Ibs. of rose-petals in 

 India, it requires a most favourable season, and the operation to be carefully per- 

 formed. According to Donald Munro, the otto is procured without distillation, 

 merely by macerating the petals in water ; and in India it is sometimes thus pre- 

 pared: the roses macerating in water are exposed to the sun, when the oil separates 

 and floats on the water. It has also been said to be obtained at Damascus, and other 

 parts of Asia Minor, by the dry distillation of the rose at the temperature of a salt- 

 water bath. 



It has little colour. It is combustible ; and its vapour forms with oxygon an 

 explosive mixture. Its specific gravity at 90 Fahr. is 0-832. At 57 Fahr., 1,000 

 parts of alcohol (specific gravity 0'806) dissolve 7 parts ; and at 72 Fahr., 33 parts 

 of otto. 



Otto of roses consists of two volatile oils : one solid and the other liquid at ordi- 

 nary temperatures, in the proportion of about one of the former to two of the latter. 

 To separate them, the otto must be frozen, and compressed between folds of blotting- 

 paper, which absorb the liquid, and leave the solid oil. They may also be separated 

 by alcohol (of specific gravity 0-8), which dissolves the liquid and scarcely any of the 

 solid oil. The solid oil, according to Saussure, contains only carbon and hydrogen, 

 and these in equal number of atoms, and is therefore isomcric with oil of turpentine ; 

 it occurs in crystalline plates, fusible at 95 Fahr. The liquid oil has not been care- 

 fully examined ; it is uncertain whether it contains nitrogen, or only carbon, hydrogen, 

 and oxygen. 



Turkey supplies the commercial world with otto of roses. The rose-farms are 

 principally situated in the low countries of the Balkan between Selimno and Carloya 

 as far as Philippolis in Bulgaria. It is the Christian inhabitants of this district that 

 are chiefly engaged in the business. 



Kizaulik in Roumclia is the head-quarters of the trade. Turkey yields from 50,000 

 to 75,000 ounces per annum. The average importation of otto of roses into Britain is 

 12,000 ounces, very nearly the whole of which is from Turkey. 



A small quantity of otto of roses is prochiced iu the south of France and in Savoy 

 and the Italian borders. 



Pure Turkish otto of roses congeals at + 58 Fahr., and boils at 432 Fahr. Italian 

 otto of roses congeals at -f 62 Fahr. A sample otto of roses produced from English- 

 grown roses at Mitcham, remained solid at + 70 Fahr., but above that temperature 

 at once became liquid. 



Otto of roses, like other articles that are of value, is systematically adulterated, 

 principally with essence of geranium ; when this is the case, tho boiling-point is 

 lowered, and the congealing-point raised. The insertion of a sample of otto in a 

 bottle into water cooled with ice is a very good physical test of purity. Spermaceti 

 was at one time used to sophisticate otto, but its insolubility in alcohol rendered it too 

 easily detected. 



OUT-CROP. A geological and mining term, to signify that the edge of any 

 inclined stratum, bed of coal, or mineral vein, comes to the surface. 



OXAJLATES are saline compounds of the bases with oxalic acid. 



