One of the main obstacles to the wider application of chitin in polymeric materials is its poor tractability due to unfavorable solubility properties. The solubility can be enhanced by introducing bulky acyl residues into the polymer (as in butyrylchitin and valeroylchitin). However, if modification is carried out with shorter-chain carboxylic acids (as in acetyl-chitin), the solubility remains poor. By substituting the acetyl residues partially by butyryl residues (mixed ester formation), exclusive use of the bulky carboxylic acids can be avoided and yet good solubility is achieved. These relationships were shown by using high molecular weight mixed chitin eaters, prepared with methanesulfonic acid as the solvent and catalyst. The mixed chitin esters, varying both in the overall degree of substitution (1.5-1.9) and the molar ratios of butyryl-to-acetyl residues (1 : 0.62 to 1 : 0.72), were characterized by IR spectroscopy, DSC, elemental analysis, and H-1-NMR spectroscopy (in trifluoromethanesulfonic acid); the latter allowed the degree of substitution to be determined as well as the molar ratio of butyryl-to-acetyl residues.