(n-C12H25NH3)(2)MnCl4 and (n-C16H33NH3)(2)MnCl4 were synthesized and a series of their mixtures C12Mn-C16Mn prepared. The binary phase diagram of C12Mn-C16Mn mixtures was established by differential thermal analysis (DTA) and X-ray diffraction (XRD). A new material of (n-C12H25NH3)(n-C16H33NH3)MnCl4 and two eutectoid invariants were observed, and the two eutectic point temperatures are about 317 and 304 K. In comparison with other similar system, there are three noticeable solid solution ranges (alpha, beta, gamma) at the left boundary, right boundary, and middle of the phase diagram, respectively. (C) 2007 Elsevier B.V. All rights reserved.