168 ECONOMIC GEOLOGY 



the waste heaps of exhausted copper mines. (4) Some mines are 

 worked solely for the arsenopyrite which they contain. The 

 mineral is then concentrated, not roasted, and sold direct to the 

 refineries. (5) Some mines are worked for the arsenopyrite which 

 is concentrated and manufactured into commercial white arsenic 

 at the mine. 



In the arsenic industry various samples of the roasted ore are 

 analyzed in order to keep the product uniform in arsenic content. 

 For any arsenic found above a fixed minimum the men are sub- 

 jected to a reduction in their wages. Good work is the result. 

 Arsenic is obtained from speiss that is formed in lead furnaces. 

 This is said to have been the source of the arsenic sometimes 

 present in sulphuric acid. 



Uses of Arsenic. Arsenical compounds have acquired great 

 notoriety because murderers and suicides have successfully re- 

 sorted to them to accomplish their foul designs. Their toxic 

 nature has become so pronounced that not only the general pub- 

 lic but scientific and medical circles have become accustomed to 

 avoid such substances and to overlook some of the good qualities 

 which arsenic possesses. The layman knows very little of the 

 sources of the arsenic supply, of the manufacture of arsenical 

 compounds, and of the properties of the finished product. 



Arsenic is used in producing colors too extensively utilized for 

 the public good. Potassium arsenite was formally used for tinting 

 wall paper. This use is now practically controlled by law, only 

 a minimum per cent, per square yard of wall paper is permissible. 

 From dampness or other causes a mould is developed and hydro- 

 gen is set free which reacts upon the arsenical compound in the 

 paper and forms the deadly arsenureted hydrogen, AsHs. 



Arsenic is used in the calico printing as a conveyor, or fixer, or 

 both, of the aniline colors. It does not enter into the color largely 

 if at all for it is washed out of the calico during the process of 

 coloring. Some attempts have been made to recover the arsenic 

 from the resulting solution but the processes instituted are too 

 expensive. Realgar is utilized in the various red shades of 

 fabrics, orpiment in the production of various shades of yellow. 

 Grays may also contain arsenic. Perhaps the most dreaded of all 

 colors on account of its arsenic is the terra cotta red. Various 

 parties concerned directly in the manufacture of tinted papers 

 and colored fabrics either mine or import, or both, realgar and 

 orpiment for use as a pigment in their industries. 



