Organic acids are working solvents for a number of proteins, notably the collagens. The mechanism of solubilization can be assumed, as a first hypothesis, to consist of a weakening of salt bonds such that chain-chain interactions are lessened and dispersion can occur. However, this cannot be exclusively true since, in the case of the collagen, it has been pointed out (Gustavson 1956) that this protein is soluble in acetic acid (pK=4·76 at 25°C.) and citric acid (pK1 = 3·13; pK2=476; pK3=6·39, at 25°) but not in hydrochloric or mineral acids of equivalent or greater hydrogen ion concentration. The hydrogen ion is thus not the dominant solubilising factor. The same author suggested that the unionized organic acids were bound by peptide bonds of proteins in such a way as to wedge apart the associated chains.