How to Test Gold, Silver and Other Precious Metals.

Gold jewelryTo start, make three test solutions as follows:

  1. Bottle #1: Schwerter's Testing Solution - Mix 1 gram of Potassium Dichromate with 22ml of concentrated Nitric acid and 8ml distilled water.
  2. Bottle #2: Mix 1 part (by volume) Hydrochloric acid and 50 parts of Nitric acid. Add to 12 parts of distilled water.
  3. Bottle #3: Aqua Regia - Mix by volume - one part Nitric acid to 3 parts Hydrochloric acid. Caution!! Aqua regia is highly corrosive. Freshly prepared it is colorless, but turns orange within seconds. It decomposes rapidly so only mix a small batch for testing.

GOLD TESTING

Pure gold is very soft. To make it more useful it is hardened by alloying it with other metals. Pure (or fine) gold is 24 carat; 14 carat is 14/24 (58%) gold by weight, the balance an alloy metal.

Test to distinguish gold from non-gold:

  • File a notch in the piece to be tested.
  • Apply a drop from Bottle #1

Results:

A bright green reaction indicates gold plate on copper or brass. A pinkish cream color indicates gold plate on silver.

Test to distinguish gold carat values:

  • File a notch in the piece to be tested. 
  • Apply a drop from Bottle #1. Ten carat gold will show a slight reaction, over 10 carats, little or no reaction.
  • Apply a drop from Bottle #2. Fourteen to 18 carat will show a slight reaction, over 18 carat, little or no reaction.
  • Apply a drop from Bottle #3. Over 18 carat will show a slight reaction.

SILVER TESTING

Pure silver is almost perfectly white, and very malleable. Because pure silver is too soft for practical use it is usually combined with copper to harden it. Sterling silver is 92.5% silver and 7.5% copper by weight. Mexican silver is typically less than 90% pure silver.

Test for silver:

  • File a notch in the piece to be tested.
  • Apply a drop from Bottle #1

Results:

  • Sterling silver turns cloudy cream. A green reaction indicates plated ware.
  • Pure silver turns bright red
  • Silver (92.5%) turns dark red
  • Silver (80%) turns brown
  • Silver (50%) turns green

OTHER METALS

Using Bottle #1 and above procedure look for the following reactions.

  • BRASS - Dark brown
  • COPPER - Brown
  • NICKEL - Blue
  • LEAD - Yellow
  • TIN - Yellow
  • PALLADIUM - None