ASSAY METHOD OF CUPELLATION FOR GOLD- AND SILVER-CONTAINING LEAD ALLOYS Russian patent published in 2004 - IPC

FIELD: analytical methods.

SUBSTANCE: dripping is charged into working chamber of electric oven and heated to 930-1000^оС, after which lead alloy is added. Alloy is subjected to oxidative fusion to achieve residual weight 1.5 to 4.5 g. Oven temperature is then lowered to 900^оС and cupellation is completed at this temperature. After that, dripping is removed from the electric oven, cooled, freed of gold/silver alloy, and weight of gold and weight of silver in the dripping are determined. For that, one measures diameter of spot formed on dripping under gold/silver alloy. When cupellation process is performed properly, following calculation relationship should be fulfilled: d_meas ≤ D_permit = k·M1/4Ag

, where D_permit is permissible spot diameter, mm; k coefficient of proportionality, mm/mg^1/4, whose value for magnesite fields equals 1,5; and M_Ag is weight of silver in regulus, mg. Novelty resides in that temperature conditions of the cupellation in the two first periods are 930-1000^оС, indirect indication allowing estimation of the quality of performing cupellation procedure is diameter of spot, and use of calculation formula for estimating above quality.

EFFECT: expanded analytical possibilities.

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