The meconic acid group of substances has always been regarded as peculiarly interesting. Situated, as it is, on the ill-defined limits of the fatty and aromatic compounds, and exhibiting interesting isomeric relations with other organic substances, the structure and derivatives of the whole group afford ample scope for theoretical speculation. Meconic acid has always been considered a tribasic acid, which, by the successive elimination of two molecules of carbonic anhydride, yields first a dibasic and then a monobasic acid. But chemists now know that the basicity of an acid may be less than its atomicity, and that even the former cannot be deduced from the composition of one or two isolated salts, but only from a comprehensive view of all the salts and ethers of the acid. As now a general review of the salts and ethers of meconic acid seems to point to an acid with an atomicity greater than its basicity, and as any additional proof of this constitution would help to explain many abnormal decompositions in the series, the authors have investigated the action of the general reagents on these compounds that enable us to distinguish between the basic and alcoholic hydroxyls.