Identification of white jewelry alloy based on silver and platinum for testing purposes

Tatyana Artyukh,Svitlana Yaheliuk,Mihai Cernavca,Oleksii Verenikin,Inna Hryhorenko,Alla Ternova

doi:10.15587/1729-4061.2021.243179

Abstract

The procedure for the identification of white jewelry alloys based on precious metals, in particular, silver, platinum and platinum group metals with different contents of alloying components, by testing on an assay stone and by the method of X-ray fluorescence analysis has been considered. The methodology for assessing the compliance of silver and platinum fineness in white jewelry alloys of different component composition with the requirements of regulatory documents and the procedure for their identification has been improved. It has been established that the silver fineness in precious alloys of the AgCu, AgZnCu system, determined using the potassium dichromate reagent on the test stone, depends on the manifestation of the contrast of the qualitative reaction from the standard sample (assay needle). It has been proven that for testing silver alloys containing palladium, the "Acid reagent for gold 750" is effective, which works to determine the qualitative and approximate content of silver in alloys. It was determined that the reagent "Ferrous-cyanide potassium" is very sensitive to changes in the alloy composition of silver alloys and makes it possible to establish the silver content with an accuracy of 5 %. The presence in silver alloys of such impurities as zinc, cadmium, nickel, gold, palladium and others increases the error in determining the fineness of silver and forms a different color and shade. It has been proven that testing of silver alloys on an assay stone with silver nitrate is effective only for the СрМ system. The presence of zinc in 925 sterling silver alloys visually increases the color intensity of the sediment, which indicates a higher overestimated fineness. It has been found that the identification of the content of precious alloys based on platinum for the presence of ligature components is carried out with a potassium iodide reagent at t=120 °C by the color and shade of the sediment. The procedure for using potassium iodide during testing of precious platinum-based alloys has been optimized

Highlights

Precious white metals, in particular silver, platinum, palladium, rhodium, have long been successfully used in the manufacture of exclusive jewelry, household items for table setting, clocks, ritual, church and cult things, coins, etc
It has been established that accurate fineness determination, with the appearance of a characteristic colored sediment, depending on the composition of silver precious alloys on test stones, is effective through the use of a number of reagents
The zinc content of 925 silver alloys visually increases the color intensity and the amount of sediment, acquiring a blue tint. This indicates a higher sample compared to the color intensity of the sediment of the standard alloy and the results of X-ray fluorescence analysis (XRF)

Summary

Introduction

In particular silver, platinum, palladium, rhodium, have long been successfully used in the manufacture of exclusive jewelry, household items for table setting, clocks, ritual, church and cult things, coins, etc. The main advantages of jewelry platinum in comparison with gold are its rarity, noble white color and luster, high resistance to chemicals and air. Due to the high strength and toughness of the metal, the products do not change their properties during operation and practically do not wear out. In terms of resistance to tarnishing in air, jewelry palladium is almost as good as platinum and has a number of additional advantages: more intense white color, better pressure-processed, cheaper. Low resistance to chemicals and external influences, a significant part of silver jewelry is made with rhodium plating

Objectives

Methods

Findings

Conclusion