Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/697

Rh the term arsenic is more frequently applied to arsenious acid (the white arsenic of commerce) than to the metallic element to which it strictly applies. Although not very abundant, arsenic is one of the most widely disseminated of all metallic elements, few sulphur ores being free from traces of it. Metallic arsenic is found native in veins in metamorphic rocks in the mining districts of Saxony and Bohemia, and other European localities, at Zmeov in Siberia, and very abundantly in the silver mines at Chanarcillo in Chili. The ores employed in the metallurgy of arsenic are mispickel or arsenical pyrites, smaltite, and cobaltite ; the arsenic in the case of the two last being a bye-product of the preparation of cobalt and nickel. Arsenic is a highly brittle metal of a steel-grey colour, and of no very great importance in the arts. It may be prepared direct from arsenical pyrites by subliming in closed retorts, but it is more commonly reduced with powdered charcoal from arsenious acid. The physical characteristics of the metal vary according to the mode of its preparation ; that produced directly from pyrites being compact, crystal line, and nearly white, while the metal reduced from arsenious acid is grey and pulverulent. It is chiefly used for mixing with lead in the manufacture of small shot, the alloy dropping in rounder forms than pure lead, which pro duces tailed drops. Arsenic is added to iron and steel for the manufacture of chains and ornaments, the resulting combination taking a very brilliant polish ; and an alloy of copper and arsenic produces a brittle grey metal of a brilliant silvery hue, used in the manufacture of buttons. Arsenious acid, or more properly anhydride, the arsenic or white arsenic of commerce, is the form in which arsenic is chiefly produced in metallurgical operations. It is found native to a small extent, and known by the mineralogical name arsenite. The greater proportion of arsenious acid is obtained as a bye-product of the reduction of cobalt and nickel from their ores. At Reichenstein in Silesia, and Pdbas in Catalonia, mispickel is worked for arsenic. From the returns received at the English Mining Record Office it appears that 5449 tons of arsenic were produced in England in 1873. More than one-third of this came from one mine in Devonshire, where the arsenical pyrites is converted into white arsenic by roasting. In the re duction of the ores, which is accomplished in reverbera- tory furnaces, special precautions have to be employed to defend the workman against arsenical fumes and dust. The arsenic is obtained as an impure white powder, which is sublimed till sufficiently pure ; and thereafter, by sub limation at a high temperature, the product is formed into a glassy mass. This glass is at first perfectly transparent, but it soon assumes the opaque white appearance arsenic presents in commerce. Besides being the basis of most arsenical preparations and compounds, it is used in the manufacture of glass for reducing the iron oxide contained in sand. White arsenic is one of the most violent of the acrid poisons. Its toxicological relations, the tests for it, &c., will be treated of under. Arsenic acid is prepared from arsenious acid on the manufacturing scale by oxidising with strong nitric acid. It also is poisonous, but to a less degree than arsenious acid; and it is noticed that people employed about it become very fat, without any injury to health being appar ent. It is now very extensively employed in the manufac ture of aniline dyes, and also as a substitute for tartaric acid in discharging colours in calico printing. Both arsenite and arseniate of soda are used as &quot; dung-substitutes &quot; in calico-printing. Scheele s green is an arsenite of copper, and Schweinfurth green is the aceto-arsenite of copper. Both are brilliant green pigments in extensive use, and their employment by paper-stainers has caused a good deal of excitement and unnecessary terror. The rubbing off of arsenical particles in cleaning wall-papers may be injurious to health, but there is no possibility of any arsenical exha lation arising from the walls as has been alleged. Two sulphur compounds of arsenic realgar and orpi- ment are also of industrial importance. Realgar, or ruby sulphur, is the disulphide of arsenic ; and in its native form it was known to the ancients, being the crai Sapa/o; of Theophrastus. It is prepared usually from arsenious acid by mixing and melting it with the required proportion of sulphur. It is used only to a limited extent as a pigment, and is a constituent of the Indian white fire used in fire signals and pyrotechny. Orpiment (auripiymen- tum), the yellow sulphide of arsenic (the dporevi/cov of Dios- co rides), occurs native in many localities. It is, like realgar, artificially prepared by mixing arsenious acid with the requisite quantity of sulphur, and subliming the mixture. Sulphur is used in proportions varying according to the depth of yellow desired, the orpiment of commerce not being a definite chemical compound, but a mixture of arsenious acid and the yellow sulphide, the light tints sometimes containing as much as 97 per cent, of white arsenic. It forms the artists colour called king s yellow ; and in addition to some use as a common pigment, it is employed in dyeing and calico-printing. The preparations of arsenic used in pharmacy, in addition to arsenious acid, are Liquor arsenicalis, or Fowler s solution, the hydro chloric solution of arsenic, arseniate of iron, and the arse niate of soda.  ARSON has been defined as the malicious and wilful burning of the house of another, and is at common law an offence of the degree of felony. Some part of the house must be actually burnt ; a bare intention or attempt will not constitute the offence, but the burning of any part, however trifling, is sufficient. The burning must be mali cious and wilful. If a man by wilfully setting fire to his own house burn the house of his neighbour also, it will be felony. The word Jiouse, in the definition of the offence at common law, extends not only to dwelling-houses, &quot; but to all out-houses which are parcel thereof, though not adjoining thereto.&quot; Barns, with corn and hay in them, though distant from a house, are within the definition. The different varieties of the offence are specified in the statute 24 and 25 Viet. c. 97 (Malicious Injuries to Pro perty Act). The following crimes are thereby made felonies : (1.) Setting fire to churches or other places of divine worship ; (2.) Setting fire to a dwelling-house, any person being therein ; (3.) Setting fire to a house, out house, manufactory, farm-building, &c., with intent to impose and defraud any person ; (4.) Setting fire to build ings appertaining to any railway, port, dock, or harbour ; or, (5.) Setting fire to any public building. In these cases the Act provides that the person convicted shall be liable, at the discretion of the court, to be kept in penal servitude for life, or for any term not less than three years (now jfa^ years by the 27 and 28 Viet. c. 47), or to be imprisoned for any time not exceeding two years, with or without hard labour, and with or without solitary confinement, and, if a male under sixteen years of age, with or without whipping. Setting fire to other buildings, and setting fire to goods in buildings in such circumstances that, if the same were thereby set on fire, the offence would be felony, are subject to the punishments last enumerated, with this exception, that the period of penal servitude is limited to fourteen years. The attempt to set fire to any building, or any matter or thing (as in last offence), is to be punished in the same way. So also is the crime of setting fire to crops of hay, grass, corn, &c., but setting fire to stacks of tho same, or any cultivated vegetable produce, or to peat, coals, itc., is regarded as a more serious offence, and the penal servitude may be for life. For the attempt to commit the 