182 REPORT OF NATIONAL MUSEUM, 1899. 



3. Arsenic. 



This substance occurs native in the form of a brittle, tin-white metal, 

 with a specific gravity of 5.6 to 5.7 and a hardness equal to 3.5 of the 

 scale. On exposure it becomes dull black on the immediate surface. 

 It is found, as a rule, in veins in the older crystalline rocks associated 

 with antimony and ores of gold and silver. Some of the more cele- 

 brated localities for the mineral, as given by Dana, are the silver mines 

 of Freiberg (Specimens Nos. 60924 and 67730, U.S.N.M.), Annaberg, 

 Marienberg, and Schneeberg in Saxony; Joachimsthal in Bohemia; 

 Andreasberg in the Harz; Kapnik and Orawitza in Hungary; Kongs- 

 berg in Norway; Zmeov in Siberia; St. Maria aux Mines, Alsace; 

 Mount Corna dei Darden, Italy; Chanarcillo, Chili; San Augustin, 

 Hidalgo, Mexico, and New Zealand. In the United States it has been 

 found at Haverhill, New Hampshire; Greenwood, Maine; near Lead- 

 ville, Colorado; and on Watson Creek, Frozen River in British 

 Columbia. 



The arsenic of commerce is, however, rarely obtained from the 

 native mineral, but is prepared by the ignition of arsenical pyrites 

 (FeAsg) or arsenical iron pyrites (FeS2,FeAso). The white arsenic of 

 commerce (arsenious acid, As.,03), though occurring sometimes native 

 as arsenolite in the form of botryoidal and stalactitic crusts of a white 

 or yellowish color, is, as a rule, obtained as a by-product in the metal- 

 lurgical operations of extracting certain metals, particularly cobalt 

 and nickel, from their ores. Such ores as niccolite, a nickel arsenide 

 (NiAs), gersdorffite (NiAsS), Rammelsbergite (NiAs^), Smaltite 

 (CoASj), Skutterudite (CoAsj), Proustite (AgjAsSs), and other arsen- 

 ides and sulpharsenides on roasting give up their arsenic in the form 

 of fumes, which are condensed in chambers prepared for this purpose. 

 Uses. — Arsenic is utilized in the form of arsenious acid (As^Og) in 

 dyeing, calico printing, in the manufacture of various pigments, in 

 arsenical soaps, in the preparation of other salts of arsenic, and as a 

 preservative in museums, particularly for the skins of animals and 

 birds. 



4. Allemontite. 



Allemontite, or arsenical antimony of the formula SbASj, = arsenic 

 65.2; antimony 34.8, occurs somewhat sparsely at AUemont in France, 

 Pribram, Bohemia, and other European localities associated with 

 sphalerite, antimony, etc. (Specimen No. 67728, U.S.N.M.). So far 

 as the writer has information the mineral has not as yet been found 

 in sufhcient quantity to be of economic value. 



