Start with 250ml distilled water.
Turn on stirrer
Add Karo, 5 drops minimum, more is ok.
Add sodium carbonate (1/4 ml).
Add 1 ml gold chloride.
Stir for 10 seconds
Put in microwave on high for 2 to 3 minutes
When color changes to ruby red, its done.
If you use enough Karo, there will be no ionic gold remaining.
You can test this by adding more Karo and watching for additional color change.