is placed on a 0 75 mm sieve sieved homogenized in a glass container in a turbula mixer as zeolite there was used a zeolite of type a wessalith u00ae of degussa ag which was was produced according to german os no 2651436 and related strack u s pat no 4 305 916 and has the particle spectrum of fig1 as synthetic silica there was employed the silica sipernat 22 u00ae of degussa ag silica sipernat 22 u00ae is a precipitated and spray dried silica having the following physical chemical properties ______________________________________surface area according m sup 2 g 190to betaverage size of the nanometer 18primary particlesaverage size of the micrometer 80secondary particlesbulk density din g l 22053 194 loss on drying din 55 291 6 2 hours at 105 u00b0 c loss on calcining din 55 921 5 2 hours at 1000 u00b0 c ph din 53 200 6 3sio sub 2 din 55 921 sup 3 98al sub 2 o sub 3 0 2fe sub 2 o sub 3 0 03na sub 2 o 1so sub 3 0 8sieve residue according 0 5to mocker din 53 580 oil number according g 100 g 230to din 53 199 ______________________________________ sup 1 based on the material dried for 2 hours at 105 u00b0 c sup.