. Transactions. iling by the addition to thebeaker of from 10 to 20 cc. of a saturated solution of ammo-nium nitrate containing 20 per cent, of free ammonia. Aftersolution the beaker is nearly filled with water, and from 10 to20 cc. of nitric acid added. The solution is now ready forelectrolysis. A wide range of current-strength is permissible,but from to 2 amperes is most satisfactory; this amountkeeps the solution sufficiently hot during the electrolysis. Atthe end of two hours, the lead is completely deposited in theform of peroxide on the anode. The anode is then removed,washed in wate
. Transactions. iling by the addition to thebeaker of from 10 to 20 cc. of a saturated solution of ammo-nium nitrate containing 20 per cent, of free ammonia. Aftersolution the beaker is nearly filled with water, and from 10 to20 cc. of nitric acid added. The solution is now ready forelectrolysis. A wide range of current-strength is permissible,but from to 2 amperes is most satisfactory; this amountkeeps the solution sufficiently hot during the electrolysis. Atthe end of two hours, the lead is completely deposited in theform of peroxide on the anode. The anode is then removed,washed in water and in alcohol, ignited and weighed. Thetheoretical factor is ; but in practice is found to bemore accurate; probably due, as Hollard says, to an excess ofoxygen in the peroxide. The accuracy of this method ranks with that of carefully-made electrolytic coppers, and its great advantage is the smallamount of the chemists time required. In the presence of THE ELECTROLYTIC ASSAY OF LEAD AND COPPER. 607. Fig. 1.—Anodes, Cathodes and Terminal Connections. 1 1 .xi;:^...- ?- j nun if rf I SI 1 *.??. *«? s* ? . «l 1 ? |i<ii( lL^HFT fll|jT ? . A ^K Fig. 2.—Electrolytic Cabinet Showing Kheostats, Voltmeter and Ammeter. 608 THE ELECTROLYTIC ASSAY OF LEAD AND COPPER. manganese or antimony, it is necessary to have a large excessof free nitric acid in the electrolyte, under which conditionneither element interferes. Bismuth, even in the presence ofvery large amounts of free nitric acid, is partly precipitated asbismuth oxide with the lead. Its presence can be recognizedby a light-blue color given to the peroxide coat. Arsenic andtellurium have to be removed before electrolysis, for, if presentin large amounts, they effectually prevent any deposition oflead. Unless the anode is sand-blasted, only a comparativelysmall amount of peroxide will adhere, but, properly sand-blasted, adherent deposits of 250 mg., and even up to 600 mg.,of peroxide may be obtained in daily work.
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
