426 



SMELTING PROCESSES AT FREIBERG. 



stirring it thoroughly when in a liquid state by means of iron roils in order to bring the impurities to the surface, 

 ■whence they can be removed. 



The desired shade of color is then obtained by adding either sulphur or metallic arsenic. 



By adding sulphur the color is made a darker red, and by arsenic a brighter red. On cooling, this material forms 

 a homogeneous mass of cherry red color. In general terms it may be stated to be a sulphide; of arsenic, in which the 

 percentages of the component elements vary according to circumstances. 



This "Bed Glass" is known in the arts as Realgar, and is worth from 12 to 15 Thalers ($!) to 11.25) per cent. 



It is used by tanners to remove the hair from the hides. 



" Yellow Glass" is also a sulphide of arsenic with a higher percentage of sulphur, and is prepared in a similar 

 manner. 



