الفهرس 
Soxhelt methodOnly 14 pages are availabe for public view
 |  | from | 140 |  |  |
| | | from | 140 | | |
Abstract
The chemical d u r a b i l i t y of glass is the r e s i t a n c e which it o f f e r s towards attack by aqueous solutiom or by atmospheric agents . Diffusion controlled ion exchange d e a l k a l i s a t i o n is the most important reactioc which occurs on attack of a l k a l i s i l i c a t e glasses by aqueous solutions. Kinetics of t h i s reaction is main object of t h i s work. A study has been made of the decomposition of a number of simple binary a l k a l i oxide-silica glass by water and d i l u t e a c i d i c s o l u t i o n . It was centred on the time and temperature dependence of dealkalisation. The decomposition experiments were c a r r i e d out f o r time durations ranging from one hour to more than two months at constant temperatures ranging between 44 and 100•‹C. The percentage of a l k a l i oxide leached out of the glass under these conditions varied between 6% and complete deal t a l i s a t i o n depending on time, temperature, composition of the g l a s s and form i n which it was leached (powder or alabs). The study is summarized i n three chapters :- Chapter I: p r e s e n t ~ a general introduction of the theory of d e a l k a l i s a t i o n i n r e l a t i o n to glass composition, temperature and time. It allso includes a summary of the action of aqueous solutiors on binary and ternary s i l i c a t e glasses with s e p a r a t e s e c t i o n s on the e f f e c t of the type and percentage of a l k a l i ion present as well as on the e f f e c t of pH of solution. This is followed by a section devoted to surveying the methods of t e s t - ing chemical d u r a b i l i t y of glass i n d i f f e r e n t solutions and recent methods used f o r testing glass surfaces. Chapter I1 : includes a description of the methods oz” synthesis and preparation of glass samples f o r - leaching aa well as the apparatus used f o r short and long durations. It also provides a description of t h e methods of analysis of a l k a l i and s i l i c a extracted in solution . Chapter 111. includes the r e s u l t s obtained and t h e i r d i s s c u s s i o n as followr~r - For short time experiments c a r r i e d out on graina of two kinds of glass (P1 5 and L ) i t was found that of 33 The r a t e of leaching a l k a l i follows the equation:. where Q is quantity of alkali extracted in time t,