292 



DISCOVERY 



When once alight these furnaces are kept going day 

 and night, Sundays and holidays, the men working 

 in shifts of eight hours at a^time, until it is judged that 

 sufficient arsenic has collected in the chambers attached 

 to the furnaces by a flue and designed for the deposi- 

 tion and retention of the arsenic vapours. The fire 

 is then drawn or the gases are diverted, by means of 

 a damper, to another " set," as a series of chambers 

 is called. 



The Refined " Soot " 



The product of this first process is arsenic soot and 

 is generally of a greyish colour, though it varies greatly 



fumes of oxide of arsenic pass up the flues to the 

 chambers, where they condense in the form of a 

 beautiful white crystalline powder on the floor, walls, 

 and ceiling. The long flues and rows of chambers are 

 quite a characteristic feature of an arsenic works and 

 contribute to the appearance of dilapidation and 

 antiquity which we have referred to, for the flues are 

 outwardly quite roughly constructed of brick or the 

 local stone, following the slope of the country-side for 

 a considerable distance upwards to the stack, where the 

 sulphur dioxide escapes into the atmosphere. The 

 object of these long flues is to retain the last traces 

 of arsenic, which would otherwise be detrimental to 



-CtEARING OUT THE ARSENIC SOOT. 



from buff to black, according to the material burnt and 

 type of furnace used. 



Arsenic soot is also obtained from other industries 

 in the neighbouring districts, coming, for instance, 

 from the roasting of tin ores before the latter can be 

 smelted. The larger smelters recover this by-product 

 in large flues designed for this purpose. Arsenic soot 

 varies greatly in the amount of white arsenic (xlsjOg) 

 it contains, but in any case it is subjected to the 

 refining process before it is placed on the market. 

 The soot is removed from the chambers and returned 

 to a similar furnace called a " refiner," where it is 

 again heated and volatilised. Here, however, smoke- 

 less coal is used so that the arsenic may not be con- 

 taminated with particles of carbon from the smoke, 

 and in the case where a round furnace is used it is 

 not'rotated and there is no raking apparatus. The 



vegetation near the works. The flues are cleaned 

 out about once a year and the arsenic profitably 

 recovered. 



The chambers where the soot or white arsenic is 

 collected are small vaulted brick rooms connected one 

 with another by an arched opening so placed that the 

 gases, in their passage from one chamber to the next, 

 strike a relatively cool wall before finding their way to 

 the exit placed in the corner diagonally opposed. As 

 the white arsenic vapburs zigzag through these 

 chambers, they condense and deposit in the form of 

 fine white crystals. Along one side of a " set " lies a 

 series of doors, which are closed with clay while the 

 process is proceeding, and are afterwards opened in 

 order to extract the arsenic. This, looking like so 

 much snow, is simply shovelled out into trollies and 

 taken off to the mill. 



