216 



ARSENIOUS ACID 



places, a is the grate; b, tho ash-pit; c, the openings for firing; d, the fire-place; 

 e, iron pots or kettles which are charged with the arsenious powder ; /, the fire-flues 



77 



80 



proceeding to the common chimney g ; A 

 iron cylinders ; i, caps ; k, pipes leading to 

 the poison-vent I ; m, openings in the pipes 

 for introducing the probing-wircs. 



The conduct of the process is as follows : 

 The pot is filled nearly to its brim with 

 3J cwt. of tho arsenic meal ; tho cylinders 

 are fitted on by means of their handles, and 

 luted together with a mixture of loam, 

 blood, and hair; then is applied first a 

 gentle, and after half an hour, a strong 

 fire, whereby the arsenic is raised partly 

 in the form of a white dust, and partly in 

 crystals ; which, by the continuance of the 

 heat, fuse together into ahomogeneous mass. 

 If the fire be too feeble, only a sublimate 



is obtained ; but if too violent, much of the arsenic is volatilised into tho pipes. The 

 workmen judge by the heat of the cylinders whether the operation be going on well or 



