CHAPTER XLVI 



THE RECOGNITION OF SUBSTANCES, II. A REVIEW OF THE 

 METALLIC ELEMENTS 



As in Chapter XXXII, so here, we assume that the specimen to 

 be identified contains a single substance. We consider first the 

 metallic elements, and limit ourselves to those that have been 

 described in the context. Our review will cover, mainly, the 

 properties of each simple metallic positive radical. 



Although arsenic has been stated to be a non-metallic element, 

 and antimony to be partially non-metallic, it is more convenient 

 in the problem of recognition to classify them with the metallic 

 elements. 



External Examination. The color is often significant. 

 Most of the common compounds of iron, nickel, cobalt, copper, 

 gold, manganese and chromium are colored (see text) . A metallic 

 luster (scrape off the tarnish) usually, though not always, indi- 

 cates a free metal or an alloy. The crystalline form should be 

 noted. The odor usually gives information about non-metallic 

 constituents (p. 377) only. As regards state, the vast majority 

 of the metals and their compounds are solids. When a liquid 

 presents itself, therefore, it is usually an aqueous solution of 

 some compound. Obtain the solid by evaporation. 



Solubility and Reaction of the Solution. Ascertain 

 whether the substance is soluble in water (p. 111). Note whether 

 the solution is acid, alkaline, or neutral in reaction (p. 369). No 

 substance can be identified by the preceding observations alone, 

 but the final conclusion as to the nature of the specimen must be 

 in harmony with them. 



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