The Potassium Halt of HexaJz ydrodioxydiboron. By RAMES CHANDRA RAY. IT has been shown in conjunction with Travers and Gupta (Pamphlet, H. K. Lewis and Co., 1916) that when magnesium boride, prepared by heating an intimate mixture of 1 part of boron trioxide with nearly 2& parts of magnesium powder at a red heat, is treated with water, hydrogen is evolved-rapidly a t first and afterwards