The tin-collection scheme for the determination of platinum-group metals, gold and silver

A comprehensive analytical scheme is presented for the determination of the six platinum-group metals, gold and silver. It is the result of the integration of separate procedures that have been described previously, in part, over the course of several years. The analytical scheme has been thoroughly tested in umpire and standards work on a wide variety of materials and, as a consequence, is of increasing interest to many laboratories. The precious metals are collected in molten tin when the sample is fused at 1200-1250 degrees with a flux containing stannic oxide, sodium carbonate, silica, borax and flour. The resultant tin alloy is dissolved and the precious metals are isolated by ion-exchange, solvent extraction and/or distillation procedures. With the exception of the usual facilities required in the fusion step of fire assaying, standard equipment can be used in the wet-chemical operations for the isolation and determination of the individual precious metals.