Abstract: The invention relates to solid block acid containing cleaning compositions comprising based on the composition A) 10-75 wt-% of at least one liquid mineral acid selected from the group consisting of phosphoric acid, sulphuric acid, sulphurous acid, and nitric acid, B) 1-60 wt-% of at least one solid organic acid with pKa at 20° C. between 1.0 and 1.1, C) 15-80 wt-% of at least one carboxylic acid selected from the group consisting of citric acid monohydrate, hydroxyacetic acid, maleic acid, succinic acid, glutaric acid and adipinic acid, D) 5-40 wt-% urea, E) 0.1-10 wt-% of at least one non-ionic surfactant, and the rest up to 100 wt-% is water, wherein the composition contains less than 1 wt-% nonylphenol ethoxylates and halogen compounds.