Kasraian K, DeLuca P P
University of Kentucky, College of Pharmacy, Lexington 40536-0082, USA.
Pharm Res. 1995 Apr;12(4):484-90. doi: 10.1023/a:1016233408831.
Utilizing differential scanning calorimetry (DSC) for tertiary butyl alcohol (TBA) solutions a phase diagram was constructed for the TBA-water system. By utilizing thermal treatment during the DSC measurements the metastable states were eliminated. The phase diagram fit that for a congruently melting compound in which compound formation occurred with a maximum at 70% TBA representing pure TBA hydrate. Two eutectics occurred at 20% (Eutectic A) and 90% (Eutectic B). A freeze-drying microscope revealed that TBA altered the crystal habit of ice. A concentration of 3% TBA was required before large needle-shaped ice crystals became evident. The addition of 10% TBA to the system resulted in even finer needle-shaped ice crystals. At the eutectic compositions (20% and 90% TBA), the frozen eutectic mixture could not be resolved with the microscope because eutectic crystals are very small. The 70% TBA solution, which corresponds to the melting of pure TBA hydrate, formed very large hydrate crystals. The rate of sublimation of the TBA and water molecules was found to be concentration dependent. At concentrations below 20% TBA (water rich portion of the phase diagram) water molecules sublimed faster while at concentrations above 20% TBA (TBA rich portion of the phase diagram) TBA molecules sublimed faster. At the eutectic A composition, both TBA and water molecules sublimed at the same rate. This may be because all of the TBA molecules are strongly associated with each other in the form of a clathrate hydrate.
利用差示扫描量热法（DSC）对叔丁醇（TBA）溶液进行分析，构建了TBA - 水体系的相图。通过在DSC测量过程中进行热处理，消除了亚稳态。该相图与一种具有一致熔融化合物的相图相符，其中化合物形成在70% TBA时达到最大值，代表纯TBA水合物。在20%（共晶A）和90%（共晶B）处出现了两个共晶点。冷冻干燥显微镜显示TBA改变了冰的晶体习性。在大的针状冰晶变得明显之前，需要3% TBA的浓度。向体系中添加10% TBA会产生更细小的针状冰晶。在共晶组成（20%和90% TBA）下，冷冻的共晶混合物无法用显微镜分辨，因为共晶晶体非常小。对应于纯TBA水合物熔化的70% TBA溶液形成了非常大的水合物晶体。发现TBA和水分子的升华速率与浓度有关。在TBA浓度低于20%（相图的富水部分）时，水分子升华得更快，而在TBA浓度高于20%（相图的富TBA部分）时，TBA分子升华得更快。在共晶A组成处，TBA和水分子以相同的速率升华。这可能是因为所有的TBA分子以笼形水合物的形式彼此强烈缔合。
