310 NATURE AND DETECTION OF METALLIC POISOSTS. 



iron wirej about three inches in length, bent twice at right 

 angles into a shape something like the letter U, but with a flat- 

 tened bottom*. Its width should be about equal to the diame- 

 ter of a common gold wedding ring ; and the two ends of the 

 bent wire must afterward be tied to a ring of this description. 

 This being accomplished, take a plate of glass not less than 

 three inches squarCj lay it as nearly horizontal as possible, and 

 on one side drop some suiphuric acid, diluted with about six 

 times its weight of water, till it spreads to the size of a half- 

 penny. At a little distance from this, towards the other side, 

 next drop some of the solution supposed to contain corrosive 

 sublimate, till the edges of the two liquids join together. 

 After this is done, let the wire and ring, prepared as above, 

 be laid in such a way, that the wire may touch the diluted acid, 

 •while the gold ring is in contact with the suspected liquid. If 

 the most minute quantity of corrosive sublimate be present, 

 the ring, in a few minutes, will be covered with mercury on 

 the part which touched the fluid. It might be proper to filter 

 the mixture before submitting it to experiment, or otherwise to 

 pour it clear from the top ; since calomel, which is so fre- 

 quently taken as a medicine, might possibly be present, and 

 give rise to these appearances. The insolubility of this sub- 

 stance, however, enables us easily to avoid it by the precautions 

 here suggested. 



///. Lead. 



Lead. 



Cautions 

 against its use, 



Although lead is not so virulent a poison as either arsenic or 

 corrosive sublimate, its effects upon the animal economy are so 

 greatly to be dreaded, that those liable to its influence in ma- 

 nufactures or domestic life, cannot be too much cautioned 

 against it. I'he use of lead, in the construction of water cis- 

 terns, pumps, and conduit pipes, would, at first thought, ap- 

 pear highly objectionable ; and in many instances it is, no 

 Why not uni- ^°"'-*-^ P''°'^^''^^^^'® ^^^"j*^''^* The reasoji of its not being uni- 

 formly injuri- formly so, has been ingeniously pointed out by Gayton de Mor- 

 cases^ *" ^^^ veau. Most mineral waters contain a greater or less quantity 

 of somx salt formed by sulphuric acid. This acid is not only 



* The Greek n is no dpubt the figure intended. 



tha 



