Conductometric study of the mixing behaviour of sodium benzoate and salicylate with an anionic surfactant sodium lauroylsarcosinate

Effects of two anionic hydrotropes – sodium benzoate (NaBz) and sodium salicylate (NaSal) – on the mixed-micelle formation with an amino-acid-based surfactant – sodium lauroylsarcosinate (SLS) – in water were investigated by the conductometric method. Specific conductivity was measured for SLS/NaBz/water and SLS/NaSal/water systems to determine the critical micelle concentration (cmc). Using the regular solution theory for non-ideal mixing, the pairwise interaction parameter, β₁₂, and micellar composition, χ, were estimated in the mixed micelle. The cmc values of the surfactant–hydrotropes mixtures were generally lower than those predicted from the ideal mixing theory. The β₁₂ values are generally negative for the two systems at all mole fractions with an average value of ?2.83 for the SLS/NaBz and ?3.31 for SLS/NaSal systems, respectively, indicative of a strong attractive interaction between the SLS/NaBz and SLS/NaSal mixed micelle. The calculated thermodynamic parameters of micellisation all indicated spontaneity in mixed-micelle formation for the systems studied.     

化学反应自发性的本质含义

结合了热力学第一、第二定律及范特霍夫等温方程,利用ΔrGm的正负来探讨“自发”一词的本质含义,并指出了高中化学教科书中对于“自发”一词的不当解释,以便在教学中更好地帮助学生将“平衡移动原理”与“化学反应进行的方向”有机结合,有利于学生化学知识体系的形成与核心素养的提升。     

Study on the difference in adsorption thermodynamics for water on swelling and non-swelling clays with implications for prevention and treatment of pneumoconiosis

Excessive inhalation of mineral dust can cause irreversible damage such as diffuse fibrosis of lung tissue. Water-based dust reduction technology can effectively control the dust concentration. The study of the interaction of water-clay mineral dust is helpful to the prevention and treatment of pneumoconiosis by water-based dust removal technology. To better understand the underlying adsorption mechanisms of water molecules on clay mineral dust, the detailed adsorption thermodynamics analysis is necessary. In this paper, we research the thermodynamics of adsorption of water molecules on swelling clay of montmorillonite and non-swelling clay of illite. First, the adsorption isotherms of water molecules on montmorillonite and illite at 293–313 K were measured by gravimetric method. Then, the key thermodynamic variables, including entropy change (ΔS), surface potential (Ω), isosteric heat of adsorption (Q_st) and variation of Gibbs free energy (ΔG), were analyzed. Results illustrate that the adsorption amount for water molecules on illite is one order of magnitude smaller than that on montmorillonite, suggesting that swelling clay plays a dominant role in water molecules adsorption process. For water molecules adsorption on montmorillonite, the contribution of secondary adsorption to total adsorption (a₂/a) is always less than 30%. For water molecules adsorption on illite, the contribution of primary adsorption to total adsorption (a₁/a) is greater than a₂/a at the low pressure region, while a₂/a can exceed 60% at the high pressure region. The difference in the uptakes of water molecules adsorption on non-swelling and swelling clays is mainly resulted from the difference in primary adsorption on two clays. The Henry’s constant (K_AA) for montmorillonite is in the range of 21.37–75.08 mmol/g/kPa, which is evidently larger than the K_AA values of 0.34–0.98 mmol/g/kPa for illite. Compared with non-swelling clay, the adsorption spontaneity degree for water molecules on swelling clay is higher, and the interaction of swelling clay-water molecules is stronger. Meanwhile, the movement of adsorbed water molecules in swelling clay is more confined than that in non-swelling clay. These findings can offer meaningful guidelines for the prevention and treatment of pneumoconiosis.     

Time Travel and the Reality of Spontaneity

Contrary to the informed consensus, time travel implies spontaneity (as distinct from chance) so that time travel can only be of the second kind.A preliminary version of this paper was presented at a Seminar on ‘Reality in Physics and Philosophy,’ S. N. Bose National Centre for the Basic Sciences, Calcutta, 24-25, Feb 1996.     

关于热力学自发过程及其判据的讨论

文章指出现有各种自发过程的判据都是在指定的约束条件下才能应用,缺乏普适性是自发过程定义多样化的引发原因。在无约束条件下将热力学第一定律代入总熵判据得出并分析讨论了总熵判据的另一种形式,结合自发过程的特点总结出了热力学变化过程中能量变化的本质,给出了自发过程的通用定义。进一步指出原总熵判据只能分辨可逆与不可逆,不能分辨自发与非自发。文章给出的总熵判据的另一种形式——封闭系统任意过程的做功能力判据具有分辨自发与非自发的能力。通过理论研讨和实际应用表明,做功能力判据与总熵判据完全等价,在相应约束条件下可还原为当前热力学中各类方向判据。填补了常见的变温过程和变压过程在以前的教科书中无自发和非自发判据的空白。以前教科书中由于自发过程定义和解释的混乱而出现的一些疑难问题,在通用定义和做功能力判据面前都能得到满意的解答。