| dc.description.abstract | A brief introduction to the subject of heterogeneous salt systems has been given in Chapter I of the thesis, with particular reference to those involving two salts possessing a common ion, in and without the presence of water. This has been followed by an outline of the scope of the present work.
It was considered desirable to ascertain the influence of the solvent medium on the formation and stability of the double salts formed between two salts having a common ion. The system (NH?)?SO?–NH?NO?–H?O–C?H?OH at 30°C promised to be a good case for such study, and so the solubility and phase relationships of this system were determined.
The binary system LiNO?–H?O has been re-examined in the present investigations due to lack of agreement in the results of previous workers regarding the number of hydrates formed by lithium nitrate and the general temperature–composition relationship prevailing in the system. The system Li?SO?–LiNO?–H?O was likewise re-examined in the present work since many of the conclusions of Massink on the 30°C isotherm of the system seemed doubtful.
The details about the thermostatic equipment, solubility apparatus, and sampling methods employed in the present investigations have been described in Part A of Chapter II. The methods used for the estimation of various constituents and the specific scheme of analysis followed for each of the phase systems studied have been elaborated in Part B. New methods giving satisfactory results were devised for the estimation of sulphate in the presence of nitrate.
In Chapter III are presented the details about the mode of study of the quaternary system and the results obtained therefrom. The individual solubilities of ammonium sulphate and ammonium nitrate were first determined at 30°C in aqueous ethanol solutions of different compositions as a preliminary to the study of the composite quaternary system. Knowledge of the quaternary system was sought by a systematic study of a series of ternary systems comprising ammonium sulphate, ammonium nitrate, and solvent having any of the compositions, namely, 25.70%, 39.60%, 73.77%, and 93.79% (weight percent) aqueous methanol and finally absolute methanol.
The factors governing equilibrium attainment during the formation of the double salts were examined. The results obtained in the system also furnished interesting data on the influence of the solvent medium on the mutual solubility behaviour of ammonium sulphate and ammonium nitrate. The point as well as the space group symmetries of the compound (NH?)?SO?·3NH?NO? were elucidated by X-ray methods.
In Chapter IV are included the results of investigations carried out in the binary system LiNO?–H?O. Examinations were made of the solids separating from lithium nitrate solutions at different temperatures above 10°C as well as the product obtained on direct desiccation of lithium nitrate trihydrate. These were done by visual, microscopic, and gravimetric methods.
The system Li?SO?–LiNO?–H?O was then studied at 30°C over all regions to investigate if any evidence could be obtained for the existence of the 8-hydrate of lithium. The melting point of lithium nitrate trihydrate and the eutectic temperature between the trihydrate and the anhydrous salt were determined by solubility, thermal, and visual methods. The temperature–composition relationship in the binary system LiNO?–H?O was then determined. The solubility curves of the two solid phases, LiNO?·3H?O and LiNO?, were traced in the temperature regions 26°C to 30°C and 10°C to 26°C respectively.
Studies were also directed on (a) the supercooling of lithium nitrate solutions with respect to lithium nitrate trihydrate, (b) the factors favouring the formation of lithium nitrate trihydrate rather than the anhydrous salt, and (c) the retention of trihydrate nuclei by anhydrous lithium nitrate even after heating the mixture to temperatures above the eutectic point (26.24°C). The melting of the trihydrate was found to occur accurately at 26.24°C. The crystal structure of the trihydrate was determined by X-ray methods.
The nature of the uncertainties in the work of Massink on the ternary system lithium sulphate–lithium nitrate–water has been explained based on the experimental results obtained in the present investigations.
In Chapter V, a critical review of the results obtained in the present investigations has been presented as Summary and Conclusions. Relevant references have been cited from literature wherever necessary. | |
