Remarks upon Arsenic. 



77 



A Aj an ordinary phial with a large mouth having a capacity of 

 from ten to sixteen ounces, in which the gas is generated ; B, a 

 tube little less than half inch in diameter traverses the cork and 

 reaches nearly to the bottom of the phial ; it is for the purpose of 

 introducing the liquid to be examined and the sulphuric acid. C, 

 another tube of a much small diameter, and bent at an obtuse 

 angle; this serves to conduct the gas into a tube D, about ten 

 inches long and an inch in diameter, filled with cotton or asbes- 

 tus. E is a glass tube, (it is to be preferred if it be of refracting 

 glass ;) its internal diameter should not be more than from one 

 twelfth to one tenth of an inch, and its extremity should be 

 drawn out to a capillary opening. F is a bent sheet of tin per- 

 forated with two holes, and which serves to support that part of 

 the tube heated by the alcoholic lamp G. 



13 



In operating with this apparatus, one fifth the capacity of the 

 phial should be left empty. The zinc and liquor to be tested are 

 first introduced. The tube E is then heated by the lamp, after 

 which we introduce slowly the sulphuric acid through the tube 

 B. The gas being generated, it first traverses the tube D, where 

 it deposits most of its moisture, as well as that portion of the 

 hquor which passes out of the phial along with the gas. The 

 gas arriving at the point of the tube E that is heated, is decom- 

 posed, and the arsenic deposits itself a httle further up the tube, 

 in the form of a metallic ring. The gas that passes out of the 

 extremity is inflamed, and any arsenic that may still remain 

 combined with it, is received on a porcelain surface. 



This is the method of operating, that seemed to the committee 

 most likely to give delicate and accurate results. They seem to 

 think that fused chloride of calcium is not to be preferred to the 

 cotton or the asbestus ; but from many experiments that I have 



