AUSENIOUS ACID 215 



rimonts were concluded. The workpeople engaged in the manufacture of Rosaniline 

 are similarly affected. 



Arsenate of Potash is prepared, in the small way, by exposing to a moderate heat, 

 in a crucible, a mixture of equal parts of white arsenic and nitro in powder. After 

 fusion the crucible is to be cooled ; the contents being dissolved in hot water, and the 

 solution filtered, will afford regular crystals on cooling. It is an acid salt, usually 

 called the binarsenate of potash. This article is prepared upon a great scale, in 

 Saxony, by melting nitre and arsenious acid together in a cylinder of cast-iron. A 

 neutral arsenate also is readily formed by saturating the excess of acid in the above 

 salt with potash ; it does not crystallise. The acid arsenate is occasionally used in 

 calico-printing, for preventing certain points of the cotton cloth from taking on the 

 mordant ; with which view it is mixed up with gum-water and pipe-clay into a paste, 

 which is applied to such places with a block. 



Arsenate of Soda. An acid arsenate of soda, prepared by heating white arsenic and 

 nitrate of soda, is now used in calico-printing. 



ARSENIC, SULPHIDES OF. See ORPIMENT ; B&ALOAB. 



ARSENIIiI.0. Ground atacamite, or native oxychloride of copper, sometimes 

 used in Chili as sand for letters. 



ARSENIOUS ACID. White Arsenic, Flowers of Arsenic. AsO* (As*O 3 ). 

 This is the white arsenic of commerce, usually called Arsenic. It is obtained in this 

 country from the arsenical ores of iron, tin, &c., and on the Continent from those of 

 cobalt and nickel. It is prepared by heating the ores containing arsenic on the sole 

 of a reverberatory furnace, through which a current of air, after passing through the 

 grate, is allowed to play. The following ores are the more remarkable of this class 

 the quantity of arsenic in 100 parts is given in each case. 



I, or arsenical iron . . . . .42-88 



Lolingite, arsenical pyrites 65'88 



Kupfernickel, arsenical nickel .... 54-73 

 Bammelsbergite, white arsenical nickel . . 72'64 

 Smaltine, tin-white cobalt . . . . . 74-22 

 Safflorite, arsenical cobalt 70-37 



In the roasting of tin ores, a considerable quantity of arsenious acid is collected in 

 the flues leading from the furnaces in which this process is effected. 



The extraction of white arsenic from the cobalt ores is performed at Altenberg and 

 at Eeichenstein, in Silesia, with an apparatus excellently contrived to protect the 

 health of the smelters from the vapours of this poisonous sublimate. 



Figs. 77 to 80 represent the arsenical furnaces at Altenberg. Fig. 77 is a vertical 

 section of the poison tower; fig. 78, a longitudinal section of the subliming 

 furnace A, with the adjoining vault B, and the poison tower in part at n; fig. 79, the 

 transverse section of the furnace A, of fig. 78 ; fig. 80 ground-plan of the furnace A, 

 where the left half shows the part above, and the right the part below the muffle or 

 oblong retorts ; B' is the upper view, B" the ground plan of the vault B, of fig. 78 ; 

 m, n, the base of the poison tower. In the several figures the same letters denote the 

 same objects ; a is the muffle ; b is its mouth for turning over the arsenical schlich, or 

 ground ore ; c, c, c, fire-draughts or flues ; d, an aperture for charging the muffle with 

 fresh schlich ; e, the smoke chimney ; /, two channels or flues for the ascent of the 

 arsenious fumes, which proceed to other two flues g, and then terminate both in h, 

 which conducts the fumes into the vault B. They issue, by the door i, into the con- 

 duit k, thence by I into the spaces m, n, o, p, q, r, of the tower. The incondensable 

 gases escape by the chimney . The cover t is removed after completion of the 

 process, in order to push down the precipitate into the lower compartments. 



The arsenious schlichs, to the amount of 9 or 10 cwt. for one operation (1 roast- 

 post, or roasting round), are spread 2 or 3 inches thick upon the bottom of the muffle, 

 and heated with a brisk fire to redness, then with a gentler heat, in order to oxidise 

 completely, before subliming, the arsenical ore. With this view the air must have free 

 entrance, and the front aperture of the muffle must be left quite open.. After 11 or 12 

 hours, the calcined materials are raked out by the mouth of the muffle, and fresh 

 ones are introduced by the openings indicated above, which are closed during the 

 sublimation. 



The arsenious acid found in these passages is not marketable till it be resublimed 

 in large iron pots, surmounted with a series of sheet-iron drums or cast-iron cylinders, 

 upon the sides of which the arsenic is condensed in its compact glassy form. The top 

 cylinder is furnished with a pipe which terminates in a condensing chamber. 



Figs. 81, 82, represent the arsenic-refining furnaces at Reichenstein. Fig. 81 shows 

 at A, a vertical section of the furnace, the kettle, and the surmounting drums or 

 cylinders ; over B it is seen in elevation ; fig. 82 is a ground-plan of the four firo- 



