Forbes R T, York P, Fawcett V, Shields L
Postgraduate Studies in Pharmaceutical Technology, School of Pharmacy, University of Bradford, UK.
Pharm Res. 1992 Nov;9(11):1428-35. doi: 10.1023/a:1015806812349.
The potassium (K), sodium (NA), calcium (CA), and magnesium (MG) salts of p-aminosalicylic acid were obtained, and their thermal behavior was characterized by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). Their crystal and molecular structures were determined by single-crystal X-ray diffraction after powder patterns had shown them to be nonisomorphous. Different degrees of hydration were observed for the solid salts, and an assessment of hydrate stability to dehydration was made from thermogravimetric studies. The onset temperature of dehydration (Tt) of each salt varied within the series and exhibited correlation with X-ray determined structure. The observed onset of dehydration of MG and CA was higher than that of NA and is consistent with stronger ion-dipole interactions for the divalent salts. Crystallographic determination of the bond lengths between the metal ion and the water oxygens were 2.4 and 2.9 A for NA, between 2.0 and 2.1 A for MG, and 2.4 A for CA. The open nature and presence of a channel feature in the structure of the sodium salt may have facilitated escape of water molecules from the crystal. Particle presentation (e.g., size, crystallinity) was also shown to affect dehydration behavior.
获得了对氨基水杨酸的钾（K）、钠（Na）、钙（Ca）和镁（Mg）盐，并通过差示扫描量热法（DSC）和热重分析（TG）对其热行为进行了表征。在粉末图谱显示它们非同晶型后，通过单晶X射线衍射确定了它们的晶体和分子结构。观察到固体盐有不同程度的水合作用，并通过热重研究对水合物脱水稳定性进行了评估。每种盐的脱水起始温度（Tt）在该系列中有所不同，并且与X射线确定的结构相关。观察到Mg和Ca的脱水起始温度高于Na，这与二价盐更强的离子 - 偶极相互作用一致。晶体学测定表明，Na的金属离子与水氧原子之间的键长为2.4和2.9 Å，Mg为2.0至2.1 Å，Ca为2.4 Å。钠盐结构的开放性质和通道特征的存在可能促进了水分子从晶体中逸出。颗粒表现（例如尺寸、结晶度）也被证明会影响脱水行为。
