Chemistry in Pictures: Chloroauric acid crystals

After many centuries of being valued for its constancy, gold has recently attracted attention for its reactivity and catalytic power. Often, the first step in unlocking the chemistry of gold is oxidizing it so that gold ions can dissolve. Of course, garden-variety acids won’t do, so Grant Wheeler, a student at Olivet Nazarene University, used aqua regia. This caustic mixture of concentrated nitric and hydrochloric acids reacts with gold to form chloroauric acid, a crystalline starting material (shown here) for gold nanoparticles and inorganic compounds. 

Submitted by Grant Wheeler