CONTRIBUTIONS TO BLOWPIPE ANALYSIS. 347 



to be tested with a small fragment of ferrocyanide of potassium (" yel-; 

 low prussiate.") If copper be present in more than traces, this re- 

 agent, it is well known, will produce a deep red precipitate. If the 

 copper be present in smaller quantity, that is, in exceedingly minute 

 traces,' the precipitate will be brown or brownish-black ; and if copper 

 be entirely absent, the precipitate will be blue or green — assuming, of 

 course, that Iron Pyrites or some other ferruginous substance is opera- 

 ted upon. In this experiment, the preliminary fusion with phosphor- 

 salt greatly facilitates the after solution of the substance in bisulphate 

 of potash. In some instances, indeed, no solution takes place if this 

 preliminary treatment with phosphor-salt be omitted. 



iO. DETECTION OF LEAD IN THE PRESENCE OF 

 BISMUTH. 



[First published in the Chemical Gazette : Sept. 15, 1848. ] 



When Lead and Bismuth are present together, the latter metal may 

 be readily detected by its known reaction with phosphor-salt in a re- 

 ducing flame — antimony, if present, being first eliminated ; but the 

 presence of lead is less easily ascertained. If the latter metal be pre- 

 sent in large quantity, it is true, the metallic globule will be more or 

 less malleable, and the flame-border will assume a clear blue color 

 when made to play upon its surface, or on the sublimate of lead-oxide 

 as produced on charcoal ; but in other cases, this reaction becomes 

 exceedingly indefinite. The presence of lead may be detected, how- 

 ever, by the following plan, based on the known reduction and preci- 

 pitation of salts of bismuth by metallic lead : a method which suc- 

 ceeds perfectly with hrittle alloys containing 85-90 per cent, of bis- 

 muth. A small crystal or fragment of nitrate of bismuth is placed in 

 a porcelain capsule, and moistened with a few drops of water, the 

 greater part of which is afterwards poured off; and the metallic 

 globule of the mixed metals, as obtained by the blowpipe, having been 

 slightly flattened on the anvil until it begins to crack at the sides, is 

 then placed in ^the midst of the sub-salt of bismuth formed by the 

 action of the water. In the course of a minute or even less, according 

 to the amount of lead that may be present, an arborescent crystallization 

 of metallic bismuth will be formed around the globule. 



