الفهرس 
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Abstract
The present this is mainly concerned towards the development of simple and accurate spectrophotometric method for thorium determination in different grades of monazite and different rock types bearing thorium using both thorin and alizarin red S dyes. Direct spectrophotometric determination of thorium was performed without the use of any separation method such as solvent extraction or ions exchange techniques. The developed method depends on the formation of triple ion association complex and was optimized by studying several parameters to reach the best conditions for complex formation. Several parameters were studied for the optimization of thorium – thorin and thoriumalizarin red S formed complexes.
The present thesis was divided into five chapters and a brief summary and conclusions which are presented in the following paragraphs.
Chapter I: Introduction
Include an introduction on the history of thorium, its abundance in earth crust, the most important thorium minerals, its physical and chemical properties, compounds, uses, isotopes, applications and its effect on human health.
Chapter II: Literature Survey
Include a literature survey on different methods of thorium determination; gravimetric, volumetric, spectrometric and spectrophotometric methods.
Chapter III: Experimental
Includes the experimental part, the materials, preparation of various stock and standard solutions, instruments used and different working procedures.Chapter IV: Results and Discussion
Includes the results and discussion; several parameters were studied for the optimization of thorium determination using both thorin and alizarin red S dyes.
Part I: Studied parameters for optimization of thorium –thorin complex
This part of the thesis includes the study of several parameters for the best optimization of thorium- thorin complex formation. The results of the previous study work of the complex formation of thorium using thorin dye were 3 M perchloric acid, thorin dye concentration was 0.05%. Calibration curve obeyed Beer’s law from 0-25ppm.
(a) The study of the developed optimum conditions favoring the formation of thorium-thorin complex was carried out and it was found that:
(1) The optimum concentration of perchloric acid was 0.2M, (pH 0.7).
(2) A buffer solution (pH 0.65) was the recommended.
(3) The maximum absorption wavelength of the formed complex was observed at 542 nm.
(4) The optimum concentration of thorin dye was 3x10-4M, and molar ratio between thorium and thorin dye was found to be L:M=3:1
(5) The complex was formed instantly and remained stable for 15 minutes.
(6) The studied complex obeyed Beer’s law up to a maximum concentration of 100 mg/l (ppm) and a minimum detectable limit of 0.5 mg/l (ppm).
(b) Studies on the influence of hydrogen peroxide as a masking agent for rare earths were studied where it was found that 3% hydrogen peroxide was sufficient for its masking.
Part II: Studied parameters for optimization of thorium –alizarin red S complex
(a) The alizarin red S dye was optimized in this work for the spectrophotometric determination of thorium. The formed complex was found to be stable and sensitive for the spectrophotometric determination of thorium.