Colours of Carboys

Carboys are jars used for display purposes in pharmacy windows. Some are made of coloured glass and others contain coloured liquids. They showed customers the purpose of the shop when few could read. The reason for their colourfulness was to attract custom. There are many explanations for the use of certain colours.

Meanings of colours

The reasons below have medical origins:

Blue and Red - represents venous (deoxygenated) and arterial (oxygenated) blood.

Green and Red - Green was used to indicate a town was healthy. Red showed the town was under quarantine.

Alchemists' colours and symbols

Carboys were produced in coloured glass and white glass that would be filled with coloured water. They often had symbols painted on in gold and black. These resembled symbols that alchemists used for metals, other chemicals, plants and geometrical symbols.

The colours of the carboys were believed to represent chemical substances in solution. Different colours were used for different minerals and elements:

• Yellow for gold
• Green for copper
• Purple for mercury

Recipes for colours

Pharmacists were proud of their carboys and placed great importance on producing the right colours to display. It was also important to have a solution that would not fade.

Below are some of the common tried and tested recipes published in the Chemist and Druggist Pharmaceutical Formulas (Volume 2) from 1898:

Amethyst

Sodium salicylate 10gr.

Tincture of ferric chloride ½ dr.

Water 2 gall.

Dissolve the sodium salicylate in the water and add the tincture.

Red

Iodine 3 dr.

Potassium iodide 3 dr.

Hydrochloric acid 10 oz.

Water 2 gall.

Dissolve the iodine and potassium iodide in 8 oz of water and dilute with the rest, to which the acid has been added.

Blue

Copper sulphate 4 oz or more

Solution of ammonia a sufficiency

Water 2 gall.

Dissolve the copper sulphate in 2 pints of water, and add solution of ammonia with constant stirring until the precipitate is redissolved, then add the rest of the water.

Emerald

Nickel sulphate 3 oz.

Sulphuric acid 6 oz

Water 2 gall.

Dissolve the nickel sulphate in the water, and add the acid, stirring constantly. Allow to deposit, and decant.