Fig. 1From: A method of diamorphine (heroin) administration for harm reductionDiamorphine (Heroin) solubility curve (grey dashed line) as a function of pH modeled using Henderson–Hasselbalch theory. Experimentally determined solubility of heroin free base is indicated as a black dot [9] and its solubility will exponentially increase as pH decreases beyond its pKa. Diamorphine pKa = 7.9 [11]Back to article page