Suppliers to the Jewellery Trade

Technical Information Sheet
Gold and Precious Metal Testing with Acids

Cautions
Avoid breathing the fumes and avoid skin contact.
Nitric Acid, Hydrochloric Acid, and Aqua Regia
are extremely poisonous and corrosive !!!!
NEVER POUR WATER INTO ACID.  YOU MUST POUR ACID INTO WATER!!

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Testing Gold
Gold Test Kit
Pre-Mixed Test Acids
 
M24 Gold Tester
 

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Testing Gold and Precious Metals with Acids

Testing for gold and other precious metals is done with acids:

   
         
Gold Testing Kit - Acid

Used properly this kit will determine whether or not an object contains precious metals such as gold, silver, platinum, palladium, or any alloy thereof.

It is necessary to obtain Nitric Acid (C.P.), Hydrochloric Acid (C.P.), and distilled water to mix the test solutions. A graduated cylinder is recommended to measure the required proportions. These items may be obtained from laboratory or chemical supply houses in large cities, or from the local drug company in smaller cities. Lacy West sells these and other acids in our showroom, but we will not ship them.

Since the testing procedure requires the use of dangerous acids, special care should be taken not to spill or allow acid to touch the skin. If acid comes in contact with the skin, wash the affected area with a mild soap and water as quickly as possible.

For appraisal and testing of gold, silver, platinum, brass, nickel and German silver. Wood case contains three acid bottles with ground glass stoppers and applicators, test stone, set of gold testing needles ,and salts for making Schwerter's testing fluid. Acid must be purchased locally.

Filling the Acid Bottles
Fill one bottle with Nitric Acid, fill the second bottle with 75% Hydrochloric Acid and 25% Nitric Acid (3 parts Hydrochloric Acid and 1 part Nitric Acid). This formula will make "Aqua-Regia". The shelf life of Aqua Regia is about 3 weeks - make a fresh solution of Aqua Regia every three weeks. The third bottle is provided as a spare.

Care of your Gold Testing Kit
Mark each side of the test stone and always use Nitric Acid on one side and Aqua Regia on the other side. Wash the test stone in clean water after each use. Residual acid from a previous test may yield incorrect results. The testing needles are not plated. The tips are made of gold wire and should have a long life.

Spare Bottle
The spare bottle can be filled with Schwerter Salts. Schwerter's Testing Fluid is made by dissolving all of the Potassium Dichromate Salt in a solution of 3/4 oz Nitric Acid plus 1/4 oz distilled water. Mix well in a glass container to dissolve the salts then fill the small bottle of the kit. This is used for testing gold below 14 karat and detecting base metals.

   
         
Testing Gold

Scratch the object with a file and apply a drop of Nitric Acid. If the object turns a bright green it is gold plated or gold filled on base metal. If the object turns a pinkish cream colour it is plated or gold filled on silver. 10 karat gold will turn dark brown. 12 karat gold will turn light brown. 14 karat or higher will have little or no reaction.

A test stone can be used to test a streak of metal laid down from the jewellery, or a small groove can be filed on an inconspicuous place of the jewellery and tested.

Finding the Karat of Gold

   
         
Testing Platinum
Rub the article on the test stone and apply a drop of Aqua-Regia. A platinum mark will remain the same white color with no reaction.

Testing Palladium
Rub the article on the test stone and apply a drop of Aqua-Regia. If it is genuine, the scratch will turn red.

   
         
Testing Silver
Scratch the article with a file and apply a drop of Nitric Acid. If it turns green, it is plated. If a cloudy cream, it is sterling or better. Remember, most Mexican silver generally contains less than 90% fine silver.
   
         
Testing Below 14 Karat and Base Metals with Schwerter Salts
File a deep notch in the test piece and apply a drop of Schwerter's Solution in the notch. The colour reaction of the solution with the metal will be as follows:
   
         
Pre-Mixed Test Acids
Pre-mixed gold, silver, and platinum test acids are available for those who do not wish to mix and handle acids. Generally a selection of these pre-mixed test acids are kept on hand to test for a variety of karats and metals. These acids can be used on test stones or directly on jewellery.

Using Pre-Mixed Acids with a Test Stone

Using Pre-Mixed Acids on Jewellery Test Acids
Easy-to-use plastic bottles with secure, colour-coded caps. Use with test stones or on a portion of the jewellery that has been sufficiently filed to reveal the base metal (if any). Pre-mixed test acids are available for 10K, 14K, 18K, 22K gold, platinum, and silver.
Gold Test Acid
 
         
Mizar Electronic Gold Tester - M24

Determines 9K, 10K, 12K, 14K, 16K, 18K, 22K, 24K gold and platinum in seconds. Two-year warranty. Auto shut-off function. LED display. Low battery indication function. Battery operated and fully portable. Maintenance free. Battery is include. The complete operating instructions are on our website.

M24 Electronic Gold Tester

M24  Mizar Gold Tester - M24      $275.00
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Replacement Acid for M24
Manufacturer states there is a six-month shelf life on these acids after opening. If one carefully expels the air out of the plastic bottles after use, the acids will last much longer.
1995  Replacement Acid for Mizar Gold Tester - M24       $49.95
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