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possible caution is therefore required in order to avoid every 

 conceivable source of error, and the necessity for this ex- 

 treme caution becomes the more peremptorily called for, in 

 those cases, (by no means few in number,) in which the 

 quantity of the substance, the presence of which is to be 

 demonstrated, is exceedingly smalt. The analyst in medico- 

 legal inquiries, therefore, ought to be enabled to assert, as 

 the results of his experiments, " that there is no substance 

 in nature hitherto discovered, capable of exhibiting the 

 same physical and chemical properties, as the material, the 

 presence of which he has detected." It is, moreover, a 

 matter of importance in inquiries of this nature, that the 

 processes employed by the analyst should be as simple as 

 possible, for this gives others a greater degree of confidence 

 in his experiments ; because it removes many of those 

 sources of error which are apt to creep in, when very com- 

 plicated and tedious processes are adopted, and this, too, 

 notwithstanding that the experiments may have been per- 

 formed by very experienced hands. It sometimes happens 

 that a body may be distinguished from all ethers with 

 which we are acquainted, by observing only a few of its 

 properties, in which case such properties will be found very 

 striking, and taken together, quite proper to the body in 

 question, and not common to it, and any other substance. 

 No one chemical property can be said to be proper to one 

 substance, although that solitary property may be of such 

 a nature as to be possessed by very few substances indeed, 

 in common with the body in question : for example, 

 metallic arsenic is volatile, and it sublimes at 356° F. 

 Now, by far the greater part of the metals hitherto dis- 

 covered are not volatile at all, except at temperatures 

 not procurable by ordinary means. This property, there- 

 fore, would distinguish metallic arsenic from the greater 

 number of other metals, but there are a few metals which are 

 volatile at temperatures obtained by ordinary means, such 



