214 ARSENIC ACID 



Tho folldwing are the principal ores of arsenic : 



Native Arsenic. The most common form of native arsenic is that of reniform and sta- 

 lactitic masses, often mammillated, and splitting off in thin successive layers like those 

 of a shell. It possesses a somewhat metallic lustre, and a tin-white colour and streak, 

 which soon tarnishes to a dark grey. Its specific gravity is 5'93. Before the blow- 

 pipe it gives out an alliaceous odour, and volatilises in white fumes. It is found in 

 the silver mines of Freiberg, Annaberg, Marienberg, and Schnecberg in Saxony ; also at 

 Joachimstahl in Bohemia, Andreasberg in the Hartz, Kapnik in Transylvania, Orawitza, 

 in the Bannat, Kongsberg in Norway, Zimeoff in Siberia, in Alsace, in Borneo, and, 

 according to Dana, at Haverhill, and at Jackson, N. H. in the United States. 



Arsenical Antimony. This mineral occurs at Allemont ; also at Przibram in 

 Bohemia, where it occurs in metallic veins associated with blende, antimony, and 

 spathic iron ; at Schladming in Styria ; and Andreasberg in the Hartz. Its com- 

 position is : Arsenic, 63*62 ; antimony, 36'38. When exposed to the action of the 

 blowpipe, this mineral emits fumes of arsenic and antimony ; and fuses to a metallic 

 globule, which takes fire and burns away, leaving oxide of antimony on the charcoal. 



White Arsenic or Arsenious Acid (Arsenolite) is often formed by the decomposition 

 of other arsenical ores, and is composed of arsenic 7576, and oxygen 24'24. It occurs 

 either in minute radiating capillary crystals and crusts investing other substances, or 

 in a stalactitic or botryoidal form. Before the blowpipe it volatilises in white fumes : 

 in the inner flame it blackens and gives out an alliaceous odour ; its specific gravity is 

 3 - 69. It is white, sometimes with a yellowish or reddish tinge, and has a silky or 

 vitreous lustre. It possesses an astringent, sweetish taste. H. W. B. 



Bealgar (anciently called Sandaraca), red orpiment, or ruby sulphur, is a sulphide 

 of arsenic, having a composition, sulphur 29-91, arsenic 70'09=AsS 2 (As'S 2 ). It 

 occurs in Hungary, Saxony, Switzerland, and China. 



Orpiment (a corruption of its Latin name, auripigmentum golden paint), yellow 

 sulphide of arsenic : its composition is, sulphur 39, arsenic 61 = AsS 3 (As J S 3 .) Burns 

 with a blue flame on charcoal, and emits fumes of sulphur and arsenic. Dissolves 

 in nitro-muriatic acid and ammonia. It is found in Hungary, the Hartz, &c. 



Both realgar and orpiment are artificially prepared and used as pigments. See 

 OKPIMENT, REAIXJAB. 



ABSENIC is a brittle metal, of an iron-grey colour, with a good deal of brilliancy. 

 It may bo prepared by triturating arsonious acid, or the white arsenic of com- 

 merce, with black flux (charcoal and carbonate of potash), and subliming in a tube. 

 If arsenical pyrites be ignited in close tubes, metallic arsenic sublimes, and sul- 

 phuret of iron remains. This metal, when exposed in the air, gradually absorbs 

 oxygen, and falls into a grey powder (suboxide). This is sold on the Continent as 

 ^fly-powder. 



To prepare arsenic on a larger scale, tnispickel, or the other ores employed, are 

 pounded; some pieces of old iron are mixed with the ore, to retain the combined 

 sulphur, and the mixture placed in retorts between four and five feet in length, to 

 which receivers are adapted. The retorts are moderately heated by a fire placed 

 beneath them ; the ores are decomposed, and metallic arsenic is sublimed and con- 

 densed in the receivers. Tho arsenic obtained in this way is purified by a second 

 distillation with a little charcoal. The atomic weight of arsenic is 75 ; its 

 symbol As. 



Arsenic is used in small quantities in the preparation of several alloys ; whilst 

 arsenious acid is employed in the manufacture of opal glass ; and is much used in the 

 manufacture of shot, to which the reduced arsenic imparts a certain degree of hard- 

 ness ; and, by preventing the distortion of the falling drops of metal, and thus securing 

 regular globules, the manufacture is greatly facilitated. It is also used in pyrotechny. 



ARSENIC ACID. AsO 5 . 3HO (H'AsO 4 ). This acid was first produced on a 

 large scale by M. G. Kopp. He employs nitric acid to convert arsenious acid by 

 oxidation into arsenic acid, and by passing the nitrous acid fumes evolved, together 

 with air, over coke moistened with water, he recovers two-thirds or three-fourths of 

 the nitric acid employed. The proportions he adopts are 303 kilogrammes (nearly 

 2} Ibs. avoirdupois each) of nitric acid of 1'35 sp. gr. to 400 kilogrammes of arsenious 

 acid, and by adding the nitric acid gradually, the oxidising action may be accomplished 

 without the application of heat. 



Arsenic acid is now almost universally employed in the manufacture of Rosanttine, 

 and is therefore an article of great consumption. It is also largely used for the white 

 discharge of Turkey red. 



M. Kopp has noticed, that without any injury to the general health, a natural ten- 

 dency to stoutness was produced whilst working with arsenic acid. In the course of 

 ten weeks, while engaged on experiments with arsenic acid, M. Kopp himself increased 

 in weight considerably more than twenty pounds, which he lost again when the expe- 



