It is upon no less authority than that of Berzelius, that such 

 prominence has been given in the tables to these characters. 

 He says, (page 122 of his work on the Blowpipe,) "The odor of 

 arsenic is so good a character, that it (the arsenic) may even be 

 detected by it (the addition of a little soda) in the small portion 

 of smalt commonly used to give a blue tinge to paper." Now 

 arsenic forms a constituent among a large portion of the volatili- 

 zable metallic minerals. An objection may be urged against 

 the use of such a character, upon the grounds of the poisonous 

 nature of the metal, but the same writer, after warning his read- 

 er against unnecessary exposure to its vapors, adds, "I confess, 

 however, that I have often been in chambers, the air of which 

 was loaded with the smell of arsenic, without having ever expe- 

 rienced any ill consequences, and I have been astonished at see- 

 ing the workmen at the silver foundries near Freyberg, daily im- 

 mersed in an arsenical atmosphere, without their health appear- 

 ing to be injured by it." The strongest argument which can he 

 urged in favor of its employment, as a character, arises out of 

 the NECESSITY which exists of noticing the arsenical odor in sub- 

 mitting minerals to the blowpipe, if that metal he present in the 

 assay. 



As our enquiry is confined to the existence of vapor which is 

 sensible either to the sight or smell, when the assay (the source 

 of it) is submitted to heat, I shall say nothing of the means to 

 be adopted to render it evident, when, without additional ex- 

 periment, it is not so, as this information is not necessary here, 

 and may be met with in the fullest detail in works which treat 

 on such subjects, particularly in that from which two quotations 

 have just been made, and in Griffin's portable volume before 

 mentioned. However, no mineral must suffer exclusion from the 

 first grand division, until it has been exposed to heat in the tube, 

 roasted on charcoal in the oxidating flame of the blowpipe, and 

 submitted to the utmost heat in the reducing flame, in all of 

 which cases the nose should be brought near the assay, while in 

 a state of ignition. The presence of volatile matter will also 

 be often indicated by the odor it imparts to the charcoal while 

 it is subliming. 



