中国分散元素富集与成矿研究新进展

本文重申了对分散元素种类的界定,将Cd、Ga、In、Tl、Ge、Se、Te和Re 8种元素作为分散元素既兼顾了传统习惯,也考虑到了地球化学性质的异同,同时也考虑了地质事实.近十年来,分散元素大规模的工业利用引发了对分散元素资源的进一步研究,新的研究成果主要包括：①分散元素可以成矿,可以形成独立和共生矿床,可以形成大型甚至超大型矿床,甚至可以形成分散元素矿集区或成矿域,这一新的进展打破了分散元素不能独立成矿的传统观念.在中国已经发现了许多分散元素独立矿床;②分散元素的富集成矿具有矿床类型和矿物类型的专属性,这意味着注意特定的矿床类型,会使找到相应的分散元素矿床的可能性增加;③发现和明确了分散元素的三种主要存在形式即独立矿物、类质同象和吸附,首次在国内矿床中发现了一系列分散元素矿物和新矿物;④Se、Tl、Cd的释放对环境的危害最主要的方式是通过污染饮用水进而影响到人类健康,其它分散元素对环境的作用目前还不十分清楚.

Low-temperature heat capacity and phase transition of n-hexatriacontane

The heat capacities of crystalline and liquid n-hexatriacontane were measured with an automatic adiabatic calorimeter over the temperature range of 80-370 K. Two solid-to-solid phase transitions at the temperatures of 345.397 and 346.836 K, and a fusion at the temperature of 348.959 K have been observed. The enthalpies and entropies of these phase transitions as well as the chemical purity of the substance were determined on the basis of the heat capacity measurements. Thermal decomposition temperatures of the compound were measured by thermogravimetric analysis. (C) 1999 Elsevier Science B.V. All rights reserved.