There are many ways to purify technical silver. Only a few of them can be used at home. One of the most common cleaning methods is cupellation - the release of impurities during the melting of silver.
Necessary
- - tin can for 1-2 liters;
- - nichrome wire;
- - sheet asbestos;
- - clay;
- - refractory clay;
- - cardboard;
- - long tongs;
- - lead.
Instructions
Step 1
Wrap nichrome wire around the jar. Dissolve the clay with asbestos chips in a ratio of 1: 5 and coat the winding with the resulting mass. Dry the muffle for 3-5 days. Place asbestos sheets on the bottom of the can.
Step 2
Stir in equal proportions of clay, fire clay and asbestos chips. Shape the working chamber (crucible) and the door of the muffle furnace 1 cm thick using a prepared cardboard mold. Wait until the chamber is dry and separate the mold from it. Place the crucible in the jar and bake for several hours before first use at 1000 ° C.
Step 3
Connect the oven to a 220 V AC power supply. After heating the oven, place technical silver and lead in the oven with tongs. Depending on the amount of impurities in the silver, you need to use from 0.5 to 8 grams of lead. Insufficient lead will result in poor separation of impurities, while too much lead will increase silver consumption.
Step 4
Lead and its oxide - lead litharge during melting are absorbed into the crucible walls. A feature of the lithosphere is that it wets the crucible and together with it, other metals and their oxides, in particular copper and nickel, are drawn into the walls. As the lead is absorbed by the walls of the chamber, the molten mass will become more shiny. Unplug the stove from the mains if there is a strong shine or a so-called "silver flash".
Step 5
Take out the silver "ball" from the crucible and clean it from slags.
