Nitric Acid (HNO3) is a very corrosive and toxic strong acid that can cause severe burns. It is also known as aqua fortis. Nitric Acid is used in rocket fuels, to help make wood look older, and is used in explosives.
It can react with metals such as copper to produce a brown toxic gas called nitrogen dioxide. It is made by reaction of nitrogen dioxide with water.
In alchemy, it is known as aqua fortis, or strong water. It can dissolve silver but leaves gold unharmed, making it a good test for gold. The term acid test came from this test.