more detail by showing particularly preferred structural variants to which the invention is not restricted and first particularly to fig1 thereof in which the same reference numerals are used for identical objects there is seen a diagrammatic side view of a tank 1 according to the prior art for a reducing agent 2 in which the tank has a side wall 3 and a base 4 the reducing agent 2 is removed from an interior 10 of the tank 1 in particular from a sump 8 through an extraction pipe 11 the tank 1 is disposed in a motor vehicle 15 fig2 diagrammatically shows a side view of a tank 1 according to the present invention the tank 1 has side walls 3 and a base 4 and the side walls 3 widen conically in the direction of the base 4 in this way the cross section 6 of the tank 1 increases in size in the direction of the base 4 the extraction pipe 11 is disposed in a sump 8 which forms the lowest point of the base 4 each of the base 4 the sump 8 and at least one side wall 3 has a respective heating unit 5 formed in a wall 16 the heating units in particular have heating circuits which can be controlled independently of one another in this case the walls 16 are formed with good heat conducting properties on the side thereof facing toward the tank.