Nitric acid is an important part of our business at MGS. Without it, we wouldn’t be able to do our super-fast assays on scrap jewelry. As we’ve written about before, nitric acid can dissolve impure precious metals. But did you know that precious metals are used to create nitric acid?
In large-scale nitric acid manufacturing, knitted platinum-rhodium gauze is necessary to catalyze chemical reactions for maximum efficiency. First, ammonia gas is exposed to air. This oxidation reaction creates nitric oxide. In order to convert as much of the ammonia as possible, the process is carried out under pressure with a platinum-rhodium catalyst. The nitric oxide goes through another oxidation process to create nitric dioxide, which is mixed with water to create nitric acid.
The design of the catalyst has undergone many revisions since its introduction in the early 20th century. Originally, a pure platinum gauze was used as the catalyst. Rhodium was later added to decrease the amount of platinum lost in the reaction. The gauze was also originally used a woven design. Since about 1990, knitted platinum-rhodium gauze has become the industry standard because it has better durability and increases the efficiency of the reaction.
Most of the nitric acid made with this process goes on to create nitrogen fertilizers and other industrial products. But, a small amount makes its way to our store so we can continue to do assays for our customers.