Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, India.
J Phys Chem B. 2011 Nov 17;115(45):13261-70. doi: 10.1021/jp206586u. Epub 2011 Oct 26.
The vaporization of solid sodium metaborate NaBO(2)(s) was studied by transpiration thermogravimetry (TTG) and Knudsen effusion mass spectrometry (KEMS). The transpiration measurements, performed for the first time on NaBO(2)(s), involved use of argon as the carrier gas for vapor transport and derivation of vapor pressure of NaBO(2)(g) (by assuming it as the sole vapor species) through many flow-dependence runs and temperature-dependence runs in the temperature range 1075-1218 K. The KEMS measurements performed in the temperature range 1060-1185 K confirmed NaBO(2)(g) as the principal vapor species over NaBO(2)(s), in accord with the previously reported KEMS studies. The values of p(NaBO(2)) obtained by both TTG and KEMS are consistent within the uncertainties associated with each method and so are the second- and third-law values of enthalpy of sublimation, the latter aspect consistently missing in all previous vaporization studies. The results of both TTG and KEMS were combined to recommend the following thermodynamic parameters pertinent to the sublimation reaction, NaBO(2)(s) = NaBO(2)(g): Log{p(NaBO(2))/Pa} = -(17056 ± 441)/(T/K) + (14.73 ± 0.35) for the temperature range 1060-1218 K; Δ(r)H°(m)(298.15 K) = (346.3 ± 9.4) kJ·mol(-1); and Δ(r)S°(m)(298.15 K) = (210.2 ± 6.8) J·mol(-1)·K(-1).
采用 transpiration 热重法（TTG）和 Knudsen 逸出质谱法（KEMS）研究了固体偏硼酸钠（NaBO₂(s)）的蒸发。首次对 NaBO₂(s) 进行的 transpiration 测量涉及使用氩气作为载气进行蒸汽输送，并通过在 1075-1218 K 的温度范围内进行许多流量依赖和温度依赖的运行，假设其为唯一的蒸汽物种，推导出 NaBO₂(g) 的蒸汽压。在 1060-1185 K 的温度范围内进行的 KEMS 测量证实了 NaBO₂(g) 是 NaBO₂(s) 上的主要蒸汽物种，这与之前报道的 KEMS 研究一致。TTG 和 KEMS 获得的 p(NaBO₂)值在与每种方法相关的不确定度内是一致的，因此升华焓的第二和第三定律值也是一致的，而这在之前所有的蒸发研究中都没有涉及。将 TTG 和 KEMS 的结果结合起来，推荐了以下与升华反应有关的热力学参数，NaBO₂(s) = NaBO₂(g)：Log{p(NaBO₂)/Pa} = -(17056 ± 441)/(T/K) + (14.73 ± 0.35)，温度范围为 1060-1218 K；Δ(r)H°(m)(298.15 K) = (346.3 ± 9.4) kJ·mol(-1)；和 Δ(r)S°(m)(298.15 K) = (210.2 ± 6.8) J·mol(-1)·K(-1)。
