Effervescent compositions and dry effervescent granules

A granular detergent composition comprising at least one detergent active ingredient and from 3% to 25% by weight of a dry effervescent granule, wherein the dry effervescent granule comprises an acid wherein the acid is a mono or polycarboxylic acid selected from the group consisting of citric acid, adipic acid, glutaric acid, 3 chetoglutaric acid, citramalic acid, maleic acid, fumaric acid, malic acid, succinic acid and malonic acid in their acidic forms, their mono-, di-, tri-salts form, their anhydrous and in their hydrated forms and mixtures thereof, a carbonate source selected from the group consisting of carbonate and bicarbonate, and a binder selected from the group consisting of cellulose derivatives, homo- and co-polymeric polycarboxylic acid and their salts, C6-C20 alkyl and alkylaryl sulphonates and sulphates, polyvinylpyrrolidones with an average molecular weight of from about 12,000 to about 700,000, copolymers of maleic anhydride with ethylene, methylvinyl ether, methacrylic acid or acrylic acid, C10-C20 mono and diglycerol ethers, and mixtures thereof, wherein said acid, carbonate source and binder are in close physical proximity and further wherein said dry effervescent granule is obtained by pressure agglomeration of said acid, carbonate source and binder, characterized in that the granular detergent composition has an Effervescence Index (EI) of at least 10, the Effervescence Index (EI) being EI = ( L × S × 100 ) M × ( NC inter + NC intra )

• wherein L is the number of acidic groups of the acid having a pKa of less than or equal to 6, S is (solubility in water of the acid in g/liter, at 25° C.)⅓, M is the molecular weight of the acid, NCinter is the density of contact points between the carbonate source and acid which are separately present in the composition per mm3, and NCintra is the weight fraction of the acid in said dry effervescent granule x the weight fraction of the carbonate source in said dry effervescent granule×12.