694 RED ORPIMENT 



buff leather, which is covered with crocus. The ornamentation of the blade by etching 

 with acid and gilding, if such be required, is the last process. See 'Manufactures in 

 Metal,' as revised by Mr. Eobert Hunt ; and ' Mechanical Manipulation,' by Holtzapffel. 



RAZOR-HONE. In the manufacturing of the razor, for the first process of 

 setting, the Charnley-Forest stone is used, but the principal part of the setting is 

 accomplished almost invariably on the German hone. Various kinds of hones are, 

 however, sold under this name, and they are of course of various qualities. See HONES. 



RAZOR-STROP. ' Perhaps for the razor-strop a fine smooth surface of calf- 

 skin, with the grained or hair side outwards, is best. It should be pasted or glued 

 down flat on a slip of wood, and for the dressing almost any extremely fine powder 

 may be used such as impalpably fine emery, crocus, natural and artificial specular 

 iron, black lead, or the charcoal of wheat-straw; . . . combinations of these and 

 other fine powders, mixed with a little grease and wax, have been with more or less 

 mystery applied to the razor-strop. The choice appears nearly immaterial, provided 

 the powders are exceedingly fine, and they are but sparingly used. 



' One side of the strop is generally charged with composition ; on the other side the 

 leatker is left in the natural state, and the finishing stroke is in general given on the 

 plain side' (Holtzapffel). The razor-strop requires to be kept very clean, and it 

 should be very sparingly used. 



REALGAR, Red sulphide of arsenic. (Arsenic rouge sulfure, Fr. ; Eothes 

 Schwefelarsenik, Ger.) This ore occurs in crystalline rocks, under the form of veins, 

 as also in volcanic districts ; for example, at the Solfatara near Naples ; or sublimed 

 in the shape of stalactites, in the rents and craters of Etna, Vesuvius, and other 

 volcanoes. Specific gravity varies from 3 - 3 to 3 - 6. It has a fine scarlet colour in mass, 

 but orange-red in powder, whereby it is distinguishable from cinnabar. It is soft, 

 sectile, readily scratched by the nail ; its fracture is vitreous and concho'idal. It 

 volatilises easily before the blowpipe, emitting the garlic smell of arsenic, along with 

 that of sulphurous acid. It consists of 70 parts of arsenic and 30 parts of sulphur. 



Nearly all the commercial realgar is an artificial product, prepared by submitting 

 arsenical pyrites to distillation, or by heating arsenious acid and sulphur in due 

 proportions. It is an energetic poison, more so than the native realgar, from the fact 

 of its containing free arsenious acid. The principal use of realgar is for fireworks. 

 White Indian fire, often used as a signal-light, contains 7 parts sulphur, 2 parts 

 realgar, and 24 parts nitre. See ARSENIC and PTEOTECHNY. 



REAL VALUE. See IMPORTS and EXPORTS. 



REAUMUR'S PORCELAIN. Glass in the process of working will often 

 acquire a peculiar opacity. This appears to depend on a physical change, since by a 

 carefully-constructed process a kind of crystallisation may be set up, producing this 

 porcellanous appearance. Reaumur endeavoured to introduce a material of this 

 description in the place of pottery : hence the name. 



RECTIFICATION is a second distillation of alcoholic liquors, to free them 

 from whatever impurities may have passed over in the first. Seo ALCOHOL and 

 DISTILLATION. 



RED, ANILINE. See ANILINE RED and ROSANILINE. 



RES CHAI.lt. An earthy ore of iron, used as a drawing material. 



REDDLE. One of the ores of iron, having an earthy texture. It is found 

 more or less mixed with earthy matter, and is used for marking sheep in some of the 

 western counties. A fine variety occurs not far from Rotheram in Yorkshire, and 

 at Wastwater in Cumberland. See IRON. 



REID EBONY. See GRENADA CROCUS. 



RED HJEMATITE. Native anhydrous oxide of iron. See HAEMATITE ; IRON. 



RED XiEAD. Minium or saturnine red. A pigment formed by exposing litharge 

 to the action of the air at a temperature of about 560, by which it absorbs oxygen. 

 See LEAD. 



RED LIQUOR, when prepared by the dyer or printer, is a liquid compound of 

 acetate of alumina, having in it a little sulphate of alumina and potash ; and is pre- 

 pared by dissolving 8 pounds of alum in boiling water, and adding to this a solution 

 of 6 pounds of acetate of lead, and stirring the whole well together. Sulphate of 

 lead is formed and deposited as a heavy mass at the bottom of the liquid. The clear 

 supernatant liquid is red liquor. 



Red liquor of commerce is a crude acetate of alumina, prepared from pyroligneous 

 acid. Seo CALICO-PRINTING. 



RED MARL. A geological term, designating the upper members of the New Red 

 Sandstone formation. 



RED OCHRE. An earthy oxide of iron. See IRON. 



RED ORPIMENT. A pigment of n deep scarlet colour, prepared by burning 

 the yellow native orpiment, a trisulphide of arsenic. See ARSENIC. 



