Abstract: Compounds of the formula ##STR1## in which R.sub.1, R.sub.2 and R.sub.3 independently of one another are hydrogen, alkyl or alkoxy and R.sub.2 additionally represents a radical of the formula ##STR2## in which R.sub.1 and R.sub.3 have the abovementioned meanings, R.sub.4 is unsubstituted or substituted phenoxy or unsubstituted or substituted amino and R.sub.5 is hydrogen or a radical of the formula ##STR3## in which R.sub.1, R.sub.3 and R.sub.4 have the abovementioned meanings and R.sub.2 ' has the same meanings as R.sub.1 and R.sub.3 are suitable development accelerators in the development of exposed, photographic materials containing silver halide.They accelerate the reduction of the exposed silver salt to silver and increase the speed of photographic material.

Abstract: Compounds of the formula ##STR1## in which R.sub.1, R.sub.2 and R.sub.3 independently of one another are hydrogen, alkyl or alkoxy and R.sub.2 additionally represents a radical of the formula ##STR2## in which R.sub.1 and R.sub.3 have the abovementioned meanings, R.sub.4 is unsubstituted or substituted phenoxy or unsubstituted or substituted amino and R.sub.5 is hydrogen or a radical of the formula ##STR3## in which R.sub.1, R.sub.3 and R.sub.4 have the abovementioned meanings and R.sub.2 ' has the same meanings as R.sub.1 and R.sub.3 are suitable development accelerators in the development of exposed, photographic materials containing silver halide.They accelerate the reduction of the exposed silver salt to silver and increase the speed of photographic material.

Abstract: A filtering apparatus for filtering a fluid comprises two coaxial walls which are provided with openings for the radially-outward passage of the fluid to be filtered, granular filtering material being disposed between the walls. The fluid to be filtered is fed into the space bounded by the inner wall and the filtered fluid is abstracted from an annular chamber disposed about the outer wall. The inner wall is formed from a series of annular inclined vanes. A rotary shaft disposed coaxially within the inner wall carries blades which project between the vanes. The blades scrape deposited matter from the vanes and also scrape the radially innermost parts of the granular filter material from between the vanes. In accordance with the method of the invention, the filter material is emptied periodically from between the walls and this emptied material and the material removed by the blades is carried to a treating station for regeneration and re-cycling to the upper end of the space between the walls.