Hydrochloric acid 20 Be° is a specific concentration of hydrochloric acid. It refers to a solution that contains 20 parts of concentrated hydrochloric acid in 100 parts of solution. The "Be" stands for "Baumé", which is a unit of measurement used to express the specific gravity of a liquid.

In practical terms, hydrochloric acid 20 Be° has a concentration of approximately 31-32% hydrochloric acid (HCl) by weight. This means that there are about 31-32 grams of HCl dissolved in 100 grams of the solution.

Hydrochloric acid is a highly corrosive and acidic substance, and handling it requires proper safety measures. It is commonly used in various industrial and laboratory applications, including metal pickling, cleaning and etching processes, chemical manufacturing, and as a reagent in chemical reactions.