Ways to Find out the 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.