Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/701

Rh CdSO 4, which is produced when the metal or its oxide is dissolved in sulphuric acid, forming crystals containing cither one or four atoms of water, the former being deposited from a boiling solution, and the latter at the ordinary temperature of the air. The uses of cadmium salts are very limited ; the sulphate is employed to a small extent as a lotion in inflammation of the eyes, similarly to the sulphate of zinc, and the iodide in photography and in medicine for the same purposes as iodide of potassium. The only compound of any real importance is the sulphide, CdS, which produces several brilliant yellow and orange colours. These are quite permanent, unlike the yellow produced by lead, chromium, or other metals, which are all more or less subject to discoloration when exposed to the action of sulphuretted hydrogen in the atmosphere. It is produced when sulphuretted hydrogen, or an alkaline sulphide, is added to the solution of any cadmium salt, as an orange-red powder, which becomes carmine-red when heated. At a white heat it melts, and solidities on cooling in lemon-yellow scales of a micaceous structure. When the precipitated sulphide is heated in hydrogen it is de composed, forming cadmium vapour and sulphuretted hydrogen, which reunite in the cooler part of the tube, producing crystals exactly similar to the native mineral greenockite. The best test for cadmium is afforded by the colour of the deposit formed on charcoal when it is volatilized and oxidized before the blowpipe flame. This is of a reddish brown colour, and usually shows the colours of thin plates from the tenuity of the film ; whereas zinc under the same conditions gives a deposit which is bright yellow while hot, but becomes white on cooling. The precipitation as a yellow sulphide from an acid solution is another distin guishing character, as sulphide of zinc does not separate except from neutral or alkaline solutions. In quantitative analysis it is always estimated as oxide, being separated from solution as carbonate by precipitation with carbonate of sodium, which is converted into oxide by calcination. Cadmium, like lead, may also be separated from its solution in acids by means of zinc, which precipitates it in a dendritic form, like the well-known lead tree. The production of cadmium is restricted to a very few loca lities. At Engis in Belgium it occurs in zinc blende to the extent of about 2 per cent. The oxide formed, together with oxide of zinc in the calcination of the blende, is in the subsequent reducing process in the ordinary Belgian zinc furnace (see ZINC), reduced and volatilized in the first period of the operation, before the heat is raised sufficiently to pro duce much zinc vapour, and the vapour, on coming in contact with the air, burns with a characteristic brown flame as dis tinguished from that of zinc, which is bluish green. The deposit formed in the condensing tubes, and in the nozzles (allonges) in front of the retorts, during this part of the process is comparatively rich in cadmium oxide, averaging about 1^ per cent. It is put aside until a sufficiency is collected, when it is enriched by a second distillation up to about 6 per cent., this second product being finally reduced by a third distillation with carbon at a dull red heat. The furnace contains fifteen retorts, four of which are reserved for the reduction of the enriched oxide. Cast- iron tubes are used, as the vapour of the metal readily penetrates clay retorts. The loss on the process is very considerable, only 30 12 per cent, of the whole amount of cadmium contained in the material treated being re covered ; 21*17 per cent, is left in the residues, and 48 &quot;71 per cent, escapes condensation. The total produce of cadmium is very small ; about one-half of the amount is produced at Engis, and the remainder in Silesia. In 1874 the production of cadmium in Lower Silesia amounted to 25 cwt, valued at 000 or about j800 per ton ; but to the small demand many works had given up the manu facture.  CADMUS, in Greek Legend, was the founder of the town of Thebes originally called Cadmeia, and according to the tradition was a son of Agenor, king of Phoenicia, whence he had proceeded to Greece in search of his sister Europa, but failing to find her had, in obedience to an oracle, settled at Thebes. He there founded a town over which he in time became king, received from the gods Harmonia, a daughter of Ares and Aphrodite, as his wife, by her had a family on whom fell hoavy misfortunes, and finally retired with her to Illyria, where they both died in peace, and were transformed into snakes which watched the tomb while their spirits were translated to Elysium. At the marriage all the gods were present, and the muses sang. Harmonia received a dress (peplos) worked by Athena, and a necklace made by Hephaestus. Their offspring were Semele, Ino, Autonoe, Agave, and a son Polydorus. On his first settle ment at Thebes, Cadmus had slain a dragon, which guarded a spring, and at the orders of Athena had sown its teeth in the ground, from which there sprang a race of fierce armed men (Spartoi). By throwing a stone among them Cadmus caused them to fall upon each other till only five survived, and they became the founders of the noblest families of Thebes. Cadmus, however, because of this bloodshed, had to do penance for a long year (i.e., eight years). Such is the legend. When Greek writers came to explain it they identified Cadmus as a Phrenician hero who had introduced into Greece the Phoenician writing, mining, and other arts or institutions of civilization. But his name is Greek rather than Phoenician, and like Cadmilus in Samothrace appears to mean &quot; order,&quot; and to indicate a person who has instituted order in a state. He may have adopted much from the early Phoenician traders ; but from the fact of Thebes having been one of the seats of the primitive Pelasgi, and from the occurrence of Cadmilus in Samothrace, also a seat of the Pelasgi, it is very probable that Cadmus was originally a purely Greek hero.  CADUCEUS ([ Greek ]), the symbol of office carried by public heralds, by Mercury (Hermes), as herald or messenger of the gods, and by Iris, Victory, and Eirene. It consisted of a staff round which two serpents were twined in a knot, their heads meeting at the top of the staff. Mercury, it was said, had seen two serpents fighting and knit together so, and had chosen this as a symbol of the quarrels which it was his duty to assist in settling. Sometimes a pair of wings are attached to the staff to indicate the speed of Mercury as a divine messenger. In the British Museum there is a bronze caduceus, found in a tomb in Sicily, which appears, from the inscription engraved on it in early Greek letters, to have belonged to a public herald of the town of Longena.  CÆDMON, or (the former way of spelling is that of Bede, the latter that of Florence of Worcester), is the name of the earliest Anglo-Saxon or Old English poet of whom we have any knowledge. The meaning of the name has been much disputed. Sir Erancis Palgrave, despairing of finding a native derivation, suggested (Archce- oloyia, vol. xxiv.) that the poet might have been so called from the Chaldaic name for the book of Genesis, which is &quot; b Cadmin,&quot; in the beginning, or &quot; Cadmon,&quot; beginning, from the opening words of the first chapter of Genesis. He thought that he might even have been an &quot; Eastern visitor,&quot; who had arrived in Britain from the East, mastered the language, and come out as a vernacular poet. A hypo thesis so fanciful as this last may be at once rejected. Another suggestion of the same lively writer connects the name with the Adam Cadmon (the primitive and ideal man) of the Cabalists. It is true that Cabalistic specula tions cannot be traced back with certainty bsyond the 9th century, but it in quite possible that the word may have