Ways to Find out the Sil­ver

Consumer Voice - - Hallmarking Of Silver -

The testing process in­cludes sampling of sil­ver from the ar­ti­cles and its ex­am­i­na­tion un­der spe­cial equip­ment to de­ter­mine its uni­for­mity; de­struc­tive testing; and as­say­ing of ran­dom sam­ples drawn from the lot. IS 2113 pre­scribes the vol­u­met­ric and gravi­met­ric meth­ods for de­ter­mi­na­tion of sil­ver in sil­ver al­loys. In gravi­met­ric method, the sil­ver sam­ple is dis­solved in di­lute ni­tric acid and then sil­ver is pre­cip­i­tated as sil­ver chlo­ride by ad­di­tion of hy­drochlo­ric acid. The sil­ver chlo­ride pre­cip­i­tate is then sep­a­rated by sin­tered glass cru­cible us­ing vac­uum pump. Sil­ver chlo­ride pre­cip­i­tate is weighed and mass of sil­ver is cal­cu­lated. In the vol­u­met­ric method, the sam­ple is dis­solved in di­lute ni­tric acid so­lu­tion and then fil­tered with stan­dard sodium chlo­ride or potas­sium chlo­ride so­lu­tion. Of late, non-de­struc­tive testing (NDT) meth­ods like x-ray flu­o­res­cence (XRF) are gain­ing ground. The XRF method is a quicker way to de­ter­mine the pu­rity of sil­ver with­out im­pair­ing the ware. The sam­ple is placed over the mea­sur­ing area/cup. Af­ter closing the cham­ber it is ex­posed to the x-ray source and sub­se­quent de­tec­tor. The sam­ple is ir­ra­di­ated by x-rays and in turn, x-rays are emit­ted from the sam­ple which are char­ac­ter­is­tic of each con­stituent el­e­ment. The tech­nique is ca­pa­ble of an­a­lyz­ing all the al­loy­ing met­als present. The neg­a­tive as­pect of such de­tec­tion is that it can pro­vide the pu­rity as ob­tained on the sur­face to a depth of 25 mi­crons only and not of the sam­ple. Fur­ther, it can pro­vide the con­tent of a spot only, There­fore, in non-ho­mo­ge­neous sam­ples the re­sult may not be re­li­able. It re­quires fre­quent cal­i­bra­tion with stan­dard sam­ples for ac­cu­racy of the re­sults.

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