Pure sulfuric acid is a thick oily liquid , which is soluble in water in all proportions. When mixed with water, a lot of heat is emitted. When water is added to sulfuric acid, the water can explode in the form of heat and spill the acid into the body. For this reason, in order to dilute the sulfuric acid , it is necessary to add it drop by drop in the water while stirring. If the mixture is too hot, wait. When it is cold, you have to add acid again.