Testing for Gold with a Blowpipe Analysis

This shows several ways to use a blowpipe for mineral analysis.

Gold is the only metal that is yellow that is not affected by normal acids or other chemicals with a few exceptions a mixture of nitric and hydrochloric acids called aqua regia is one.  Gold is also soluble in a solution of sodium or potassium cyanide.  A simple test for gold can be made using a blowpipe analysis and some nitric acid.

Step 1. First grind a small sample of gold ore to a powder in an agate mortar.

Step 2. Mix this powder with an equal amount of either borax or sodium carbonate.

Step 3. Place this powder into a recess in a charcoal block.

Step 4. Blow a hot flame onto the sample with a blowpipe.

Step 5. After the sample has melted allow it to cool.  If gold is present it will collect as a small button at the base of the melted sample.

Step 6. Dissolve the sample in water saving the part that doesn’t dissolve.

Step 7. Put the residue into a small amount of dilute nitric acid, if it is yellow in color and doesn’t dissolve it is gold.

Precautions:

Do not get any acids on you!

Cyanide is deadly poisonous, don't eat the stuff!