Mix the chromite ore sample with sodium chloride--NaCl--solution so that mixture contains 5 percent of NaCl by weight. The salt acts as a strong chlorination agent that is essential to extract the PGMs.
Dry the mixture at 180 degrees Celsius for 30 minutes. This is done to remove water that was introduced to the mixture when adding the NaCl solution.
Load the dried chromite ore NaCl mixture into a chlorination reactor, such as a horizontal static furnace, and raise the temperature to 720 degrees Celsius in the presence of nitrogen--N2.
Apply a flow of gaseous chloride and carbon monoxide at a rate of 200 milliliters per minute into the reactor for two hours. This step, also called the carbochlorination, will promote formation of metallic PGM salts. These PGM salts remain in the reactor while the interfering iron exits as a gaseous FeCl3.
Cool the reactor to room temperature after the two-hour run has ended. Flush nitrogen into the reactor during the cooling. Remove the chlorinated solid residue from the reactor into a glass beaker.
Place the beaker onto a hot plate and add 100 milliliters of 3 M HCl solution. Heat the mixture to 70 degrees Celsius for 15 minutes. This steps separates the PGMs from the chromium metal; the PGMs are dissolved into the liquid, while the chromium remains in the solid.
Filter the solution to remove the solid particles that contain the chromium metal from the dissolved PGM salts. Separate the platinum group metals by using a zinc cementation or ion-exchange procedure.