Hydrates of organic compounds. XI Determination of the melting point and hydration numbers of the clathrate-like hydrate of tetrabutylammonium chloride by differential scanning calorimetry.

A thermal analytic method using a differential scanning calorimeter has been applied to binary mixtures of water with tetrabutylammonium chloride. It has been found that this method can give the same results concerning the melting point (15.2 °C) and hydration numbers (around 30) of the clathrate-like hydrate of tetrabutylammonium chloride as those determined phase-diagrammatically. The apparent enthalpy of fusion of water which forms hydrogen-bonded water lattice in the clathrate-like hydrate has been observed to be 5.47 kJ mol−1, which is comparable with 5.20 kJ mol−1 determined by the direct calorimetric measurements of enthalpy of solution of the hydrate in water. It has been concluded that the proposed method can be applicable to many similar types of systems, including systems forming a hydrate which decomposes incongruently.