Hydrochloric acid (Hydrochloric acid) formula for HCl, relative molecular mass of 36.46. Hydrochloric acid in different concentration of hydrogen chloride aqueous solution, a colorless or yellow, stimulating odour and strong corrosion resistance. Soluble in water, ethanol, ether and oil etc. Concentrated hydrochloric acid to aqueous solution containing 38% hydrochloric acid, relative density 1.19, melting point, boiling point of 112 ℃ to 83.7 ℃. 3.6% hydrochloric acid, pH value of 0.1. Note that shouldn't be used to react with potassium chlorate preparation of chlorine gas, hydrochloric acid because can form explosive of chlorine dioxide, also cannot get pure chlorine gas.