Element 79 in our International Year of the Periodic Table series is gold. Gold compounds have been used to treat arthritis in the past. Gold is also used as a food additive and found in large quantities dissolved in the oceans.

Gold compounds were used for a number of years as an injectable treatment for arthritis. These compounds included sodium aurothiomalate and auranofin. Newer treatments with fewer side effects are now more commonly used.

Gold lead and flakes are edible and added to a range of products including cakes, pastries and vodka. Its E number in the EU is E 175. Gold is chemically inert, and when used in these forms isn’t absorbed from the digestive system into the bloodstream.

Large quantities of gold are dissolved in the world’s oceans – it’s estimated the figure could be as much as 1.5 million tons. However, this translates to a very low concentration, which is too low for economic extraction.

Another use for gold is in coloured glass. Gold nanoparticles give glass a red tint. This can be seen in some stained glass windows.

Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.