2. Effects of the exposure time in months and on changes in pH values of cotton fabric at Helwan and Alexandria Cities:

Table (3) and figs (5, 6) showed that the pH- values of the examined samples had decreased gradually for each exposure month and that a maximum was obtained in June and July and a minimum in January and February at Alexandria city. While a maximum in August and July and a minimum in December and January at Helwan city.

For the 4 monthly removed samples, the increase in the acidity of cotton fabric after exposure follows the order:

4 months < 8 months <I2 months.

It was found that there is less rate of degradation in samples exposed for more than eight months.

In addition, it is observed that the degradation of the samples exposed in Helwan is higher than the samples exposed in Alexandria. This emphasizes the effect of pollution in Helwan in degradation of samples. In other words, the atmosphere at Helwan site is highly polluted and affects considerably man's life.

These results call to the fact that. the exposed samples were seriously attacked after the monthly exposure during the summer time and that they were left considerably weak where they lost about 50% of their initial strength. Hence, when dealing with results of continuous exposure, they must be carefully examined, analyzed and evaluated.

Table (3): Monthly data of Chemical Degradation (pH values evaluation) of fabric cotton at Alexandria and Helwan Cities (Year2002/2003):

Fabr.: Fabric. G. 70 : Giza 70. Alex. : Alexandria. Helw. : Helwan