This is 10mL of 1% solution liquid Gold Chloride from Photographers' Formulary. It is traditionally used as the main component within gold toning baths, and lends a distinctive tonality to finished black and white prints, ranging from warm browns to purples, but most commonly a vivid blue. Gold chloride also adds durability and helps to protect the silver content within a print from degenerating.
UPC: 675152630018