Sulphuric Acid

(sül-fu'rik-.) (Chem.) Anhydrous S. A. (SO3), or, as it is sometimes called, S. anhydride, forms beautiful white needles like asbestos. Its affinity for water is very great, and when dropped into it it hi es like a red-hot iron. Its combination with water is called S.Acid or Oil of Vitriol (HO.SO3), which is an oily colorle liquid, boiling at 620-5°, po e ing a sp. gr. of1.84; it has a very powerful affinity for water, and when exposed to the air absorbs moisture rapidly. On this account it is of great value in the laboratory as a desiccating agent for gases. When mixed suddenly with water,the temperature rises greatly, sometimes as much as 100° C. Its affinity for water is so great that it takes it from organic substances, such as wood, sugar, ., in which it is supposed not to exist really formed but only inits elements. Under the powerful influence of the acid, these unite and are withdrawn, liberating the carbon. A drop of strong S. A. left for a few minutes on almost any organic compound carbonizes it, leaving a charred stain. Oil of vitriol di olves the anhydrous acid, forming what is known as fuming S. A. S. A. is the strongest known acid at ordinary temperatures, and it unites with all bases forming salts which are called sulphates. When added to salts of other acids it displaces them, taking po e ion of the base, except in the case of some perfectly insoluble compounds, such as certain silicates. At a high temperature, however, some other acids, such as silicic and boracic acids, appear stronger than S., as, owing to their diminished volatility, they remain fixed at temperatures at which S. A. cannot exist uncombined. [s. 867]