Hyposulphurous Acid, or HYDROSULPHUROUS ACID

H.SO,. Little known; made by treating sulphurous acid with zinc. It decomposes on standing in the air, yielding THIOSULPHURIC ACID (q.v.), then sulphur dioxide, sulphur, and water. Hypotenuse. Side of a right triangle opposite the right angle. In the plane triangle its square is equivalent to the sum of the squares on the other two sides. In the spherical triangle its cosine equals the product of the cosines of the other two sides, or the product of the cotangents of the two oblique angles.