2-氨基-4，6-二甲氧基嘧啶的低温热容和热力学性质研究

通过精密自动绝热量热计测定了自行合成并提纯的2-氨基-4，6-二甲氨基嘧啶 在78-394 K温区的摩尔热容。实验结果表明，该化合物有一个固-液溶化相变，其 熔化温度、摩尔熔化焓以及摩尔熔化熵分别为：（370.97 ± 0.02）K，（29853. 91 ± 9.25） J·mol~(-1)和（80.45 ± 0.03）J·mol~(-1) · K~(-1)。通过分 步熔化法得到样品的纯度为0.9984 (摩尔分数)和绝对纯样品的熔点为371.031 K。 在热容测量的基础上计算出了该物质每隔5K的热力学函数值。DSC技术对基固-溶熔 化过程作了进一步研究，结果与热容试验相一致。

Low-Temperature Heat Capacity and Thermodynamic Properties of 2- Amino-4, 6-dimethoxypyrimidine

The low-temperature heat capacities of 2-amino-4, 6- dimethoxypyrimidine (C6H9N3O2) were precisely measured by an automated adiabatic calorimeter in the temperature range of 78 to 394 K. The sample was observed to melt at (370.97 ±0.02) K. On the basis of the heat-capacity measurements, the molar enthalpy and entropy of the phase transition as well as chemical purity of the substance were determined to be (29853.91 ± 9.25) J·mol~(-1), (80.45 ± 0.03) J· mol~(-1)·K~(-1) and 99.84%, respectively. The thermodynamic function of the compound were derived and reported at an interval of 5 K. The further research of the melting process for this compound has been carried out by means of DSC technique. The result was in agreement with that obtained from the measurements of heat capacities.