Kulkarni Sunil D, Walimbe Prasad C, Ingulkar Rohit B, Lahase Jagdish D, Kulkarni Preeti S
Post Graduate and Research Center, Department of Chemistry, S.P.Mandali's Sir Parashurambhau College (affiliated to Savitribai Phule Pune University, formerly University of Pune), Tilak Road, Pune 411 030, Maharashtra, India.
Post Graduate and Research Center, Department of Chemistry, MES Abasaheb Garware College (affiliated to Savitribai Phule Pune University, formerly University of Pune), Karve Road, Pune 411 004, Maharashtra, India.
ACS Omega. 2019 Aug 7;4(8):13061-13068. doi: 10.1021/acsomega.9b00937. eCollection 2019 Aug 20.
A periodically precipitating system wherein interband distance successively decreases is known as revert Liesegang banding. The phenomenon is rare, and the underlying mechanism is implicit. In the present paper, the Liesegang system comprising of AgNO and KBr as the outer and inner electrolyte pair showing revert banding in agar gel by employing a 1D experimental setup is studied under varying concentrations of participating species. Revert banding was observed under all the experimental conditions. The concentrations of inner and outer electrolytes were found to play a major role in reverting since they build the ionic strength inside Liesegang tubes. We hypothesize that the band reverting is the interplay of van der Waals and electrical double-layer interactions, and hence classical DLVO (Derjaguin-Landau-Verwey-Overbeek) theory can be applied to interpret reverting. We propose that revert deposition of precipitates is the outcome of flocculation and peptization of sols, which is the manifestation of balancing attractive and repulsive interactions acting on colloidal particles responsible for band formation.
一种带间距离连续减小的周期性沉淀系统被称为反向李赛根带。这种现象很罕见，其潜在机制尚不明确。在本文中，通过一维实验装置研究了以硝酸银和溴化钾作为外部和内部电解质对、在琼脂凝胶中呈现反向带的李赛根系统，研究时改变了参与物种的浓度。在所有实验条件下均观察到了反向带。发现内部和外部电解质的浓度在反向过程中起主要作用，因为它们构建了李赛根管内部的离子强度。我们假设带的反向是范德华力和双电层相互作用的相互作用结果，因此经典的DLVO（德亚金-朗道-韦弗-奥弗贝克）理论可用于解释反向现象。我们提出沉淀物的反向沉积是溶胶絮凝和胶溶的结果，这是作用于负责带形成的胶体颗粒上的吸引和排斥相互作用平衡的表现。
