The melting point of a 10 percent solution of hydrochloric acid is -18 degrees Celsius, while the melting point of a 20 percent solution is -59 degrees Celsius. The melting point varies based on the concentration of the solution.
The melting point of a substance, also known as the liquification point, is the temperature at which a substance changes from a solid to a liquid state. A 30 percent solution of hydrochloric acid has a melting point of -52 degrees Celsius, and the melting point of a 32 percent solution of hydrochloric acid is -43 degrees Celsius. The concentration of a solution of hydrochloric acid can also be referred to as the molarity or the molar concentration.