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long series of re-agents, or, in other words, by ascertaining 

 a great many of its properties. The quantity in our posses- 

 sion may, and does frequently fall far short of the amount 

 required for the rigid demonstration. I shall give an in- 

 stance here, of the possibility of demonstrating the presence 

 of a particular substance, by a few only of its properties: — 

 " There is no substance in nature, with which we are ac- 

 quainted, possessing a solid form at the mean temperature 

 of the atmosphere, a dark steel-coloured lustrous aspect, a 

 property of volatalizing considerably below 212° F., and 

 giving by continued heat a violet-coloured vapour, except- 

 ing Iodine." But Iodine possesses also many other impor- 

 tant and interesting properties, these must be known to the 

 chemist ; they are not, however, necessary for the Toxico- 

 logist, because they cannot further assist him in his desired 

 rigid demonstration of the mere existence of the substance 

 called Iodine. Again, — " There is no substance in nature, 

 with which we are acquainted, capable of existing at 

 mean temperatures as a liquid, having a distinct metallic 

 lustre, density 1 3|- times greater than water, and perfect globu- 

 larity when submitted to the force of gravity, except Quick- 

 silver." Quicksilver, however, possesses very many other pro- 

 perties highly interesting and important to the general 

 Chemist, but a knowledge of them is not essentially ne- 

 cessary to the Toxicologist ; because, they cannot better aid 

 him in the simple demonstration of the existence of the 

 substance in question. Again, — " There is no substance 

 in nature, with which we are acquainted, having a metallic 

 lustre, a bluish colour, ready solubility in nitric acid, and 

 such solution (the acid not being in excess,) precipitable 

 white, by Sulphuric acid, black by Hydro-sulphuret of 

 Ammonia, and yellow by Iodide Potassium, excepting Lead." 

 Lastly. " There is no substance in nature, with which we 

 are acquainted, having a red colour and metallic lustre, 

 ready solubility in nitric acid, and which can be precipitated 



