Page:The American Cyclopædia (1879) Volume V.djvu/529

 CRUCIBLE CRUCIFIXION 525 This abbey, founded by Ethelbald in 716, was several times destroyed, and rebuilt each time with greater splendor. CRUCIBLE, a small vessel made of refractory materials for withstanding high temperatures, and used in metallurgic and chemical opera- tions for containing substances to be melted. The name is said to have been given to it by the alchemists, from the Latin crux, crucis, in consequence of their custom of marking it with the sign of the cross. Others derive it from the Latin crucio, to torment, because the con- tents, in the language of the same alchemists, were thus treated in the operations to which they were subjected. Crucibles are made in various forms and of different materials, ac- cording to the purposes required of them. The qualities they should possess are infusibility, capacity of bearing sudden changes of tempera- ture without breaking, resistance to the chemi- cal action of the substances fused in them, and a texture impermeable to liquids and gases. The best earthenware or porous crucibles are made of the purest clays, such as consist only of alumina and silica. The texture depends upon the degree to which the materials are pulverized. The close Wedgwood crucibles are made of the best materials finely ground ; but they do not withstand sudden changes of temperature so well as the coarser Hessian and English crucibles. The former, which have been long known as the cheapest and among the best clay crucibles, are made in the vicinity of Almerode, Germany, of an aluminous clay, mixed with quartz sand. They are three-sided at top and round below. Their composition, according to Berthier, is silica 70-9, alumina 24-8, oxide of iron 3 '3, with traces of mag- nesia. They are remarkable for withstanding sudden changes and high degrees of tempera- ture. Small ones may even be heated to red- ness and thrown into cold water without break- ing. They will soften, however, at the high heat of the furnaces in which they are used, and the coarseness of their material renders them very porous. Saltpetre and common salt, and other substances used as fluxes, are liable when fused to find their way through them. Porcelain or Wedgwood crucibles are more impervious to vapors and fluxes. The French crucibles of Beaufay are perhaps more refractory than the Hessian. They are made near Namur, of clay Without additional mix- ture of sand ; when moulded they are washed over with a thin coating of pure clay, prepared by pulverizing clay that has been baked. They are more dense than other clay crucibles, and hence better resist the passage of fluxes. Their composition is, by the analysis of Berthier, sil- ica 64-6, alumina 34'4, oxide of iron 1. The English or London crucibles are triangular or circular, and have covers of the same material. They are composed of two parts of Stourbridge clay and one of pulverized coke. The Cornish crucibles, made for the assayers of copper ores in Cornwall, have long been celebrated. They are made of Poole and Stourbridge clay, mixed with sand from St. Agnes, and ground pots. An analysis by Dr. Percy gives, in 100 parts, silica 72-29, alumina 25-32, protoxide of iron 1-07, lime 0-38, magnesia a trace, potash 1-14. Blue pots, or blflfck-lead crucibles, as they are often incorrectly called, are made of the mineral graphite or plumbago, which is com- posed of carbon with 4 to 10 per cent, of iron. The substance is finely pulverized, mixed with a third or half its weight of clay, moulded into the pots, some of which are large enough to serve for assaying furnaces, and then baked. These are excellent crucibles for resisting changes of temperature, as well as the chemical action of their contents; but their higher cost limits their use. They are used in melting cast steel in the large works where it is manufactured. They may be protected on the inside from the action of the oxides, which tend to remove the carbonaceous material, by a lining of clay or other substance. These are made of excellent quality in Boston and Jersey City. For differ- ent chemical operations crucibles made of vari- ous rnetals are employed. Those of platinum are in continual use in the operations connected with chemical analyses. But these, though they bear the highest temperature, are attacked by many substances which do not affect other metals, as silver particularly, and crucibles of this material are therefore required as oc- casional substitutes. Cast-iron crucibles are cheaply made, and are very serviceable in many assays of sulphurets especially. The iron itself serves to desulphurize the natural compound of this substance, as the carbon of the brasqued crucibles deoxidizes the oxides. Assays of galena may be rapidly made one after another in cast-iron crucibles, by introducing a portion mixed with twice and a half its weight of car- bonate of soda and fusing ; the galena is decom- posed, and sulphuret of iron is produced at the expense of the crucible ; the lead set free may be poured out, and a new portion instantly introduced, and thus the operation may be con- tinued as long as the crucible lasts. CRUCIFIX (low Lat. crucifigo, to fix to a cross), a sculptured or carved representation of the Saviour attached to the cross. The simple cross was the earliest symbol of Christianity. The sixth oecumenical council (680) ordered that Christ should be represented according to his human features, rather than in the symboli- cal figure of the paschal lamb, and in the suc- ceeding century the crucifix became common throughout the church. Crucifixes are still preserved in a museum in Rome which date from the 8th century. This image is used by few Protestants, but is placed by Roman Cath- olics in churches and oratories, especially on altars, and is sometimes worn on the person. CRUCIFIXION, the punishment of death upon the cross. It was in common use among the Egyptians, Assyrians, Persians, Carthaginians, Greeks, Romans, and other nations of antiquity. In Judea it was only exceptionally practised