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about 5% to about 60%, preferably from about 10% to about 50% of a surfactant carrier is used. Controlling the particle size both of the limescale remover acid and of the surfactant carrier is also important for achieving optimum stability. In a preferred embodiment the particle size of the limescale 5 remover acid is in the range from about 100 µm to about 500 µm and more preferably from about 200 µm to about 400 µm while the weight average particle size of the surfactant carrier is less than about 70 µm and more preferably less than about 20 µm. The preferred carrier herein is selected from alkali metal salts of strong acids, polymeric disinte› grants and mixtures thereof. Especially preferred is sodium sulphate. 

The tablet can be prepared by pre-mixing all the compo› nents and compressing the mixture in a tablet press. Accord› ing to another embodiment the tablet can be prepared by preagglomeration of the non-ionic surfactant and the carrier, admixing the limescale remover acid and detergency enzyme and compressing the mixture in a tablet press. Alternatively, the non-ionic surfactant can be preagglomer› ated with the carrier and acid. 

The present invention also encompasses a cleaning method for dishwasher and washing machine interiors, said method comprising placing the tablet of the invention in the machine interior, e.g., in the case of a dishwasher in the cutlery basket, and running the unloaded machine at high or a low temperature washing program. 

The compositions according to the present invention are designed for cleaning machine interiors. The essential com› ponents of the composition are a limescale remover acid, a non-ionic surfactant and a detergency enzyme. The compo› sition is presented in the form of tablet, having a pH, measured as a 1 % solution in distilled water at 20° C., in the range from about 1 to about 5. 

Limescale remover acids preferred for use herein are selected from water-soluble organic mono- and polycar› boxylic acids with two to six carbon atoms in the molecule and optionally substituted by one or more hydroxy groups. Suitable classes of limescale remover include alkanoic acids, hydroxyalkanioc acids, alkyl polycarboxylic acids and hydroxyalkyl polycarboxylic acids. Preferred herein are mono- and polycarboxylic acids which have a pKa value, related to the first dissociation stage of less than about 6. These include for example, adipic acid, succinic acid, tar- taric acid, malic acid, glutaric acid, citric acid and mixtures thereof. Citric acid being highly preferred. 

Inorganic acids and mixtures of inorganic acids and organic acids can also be used as the limescale remover component. The inorganic acids are specially usefull when mixed with organic acids. Examples of inorganic acids are sulphonic acid derivatives, sulphamic acid (pKa=0.1 ), hydrochloric acid (pKa<0), nitric acid (pKa<0), phosphoric acid (pKa=2.1) and sulphuric acid (pKa=0.4). Suitable sul› phonic acid derivatives include alkyl sulphonic acids and aryl sulphonic acids. Suitable alkyl sulphonic acids include Cl---C6 linear or branched alkylsulphonic acids or mixtures thereof, such as methanesulphonic acid (pKa=l.9) commer› cially available for example from Aldrich, William Blythe & Co. Ltd. or Elf. Atochem. 

Suitable aryl sulphonic acids for use herein include those of the formula: 

## DETAILED DESCRIPTION OF THE INVENTION 

wherein Rl, R2, R3, R4 and R5 are each H or SO$_{3}$H, or linear or branched C0---C4 alkyl chain; or mixtures thereof. 

Preferred arylsulphonic acids to be used are those which comprise no or only one alkyl chain. Indeed, arylsulphonic acids are particularly effective at removing limescale, which is not the case for their longer alkyl chain homologues. Also arylsulphonic acids are particularly safe to the surface treated therewith. Particularly suitable arylsulphonic acids for use herein are benzene sulphonic acid (pKa=0.7), toluene sulphonic acid and cumene sulphonic acid. Amongst these three, at equal weight %, the shorter the alkyl chain, down to no chain at all, the better the limescale removing perfor- mance. 

Suitable nonionic surfactants according to the present invention includes nonionic alkoxylated surfactants (espe› cially ethoxylates derived from C$_{6}$-C$_{18 }$ primary alcohols), ethoxylated-propoxylated alcohols (e.g., Olin Corporation’s Poly-Tergentfi SLF18), epoxy-capped poly(oxyalkylated) alcohols (e.g., Olin Corporation’s Poly-Tergentfi SLF18B-see WO-A-94/22800), ether-capped poly(oxy› alkylated) alcohol surfactants, and block polyoxyethylene› polyoxypropylene polymeric compounds such as PLU› RONIC fi, REVERSED PLURONICfi, and TETRONICfi by the BASF-Wyandotte Corp., Wyandotte, Mich. Surfac› tants suitable herein are disclosed, for example, in U.S. Pat. Nos. 3,929,678, 4,259,217, EP-A-0414 549, WO-A-93/ 08876 and WO-A-93/08874. 

The nonionic surfactants are typically present at a level of from about 1 % to about 20% by weight, more preferably from about 2% to about 18% by weight, most preferably from about 4% to about 15% by weight of composition. 

Enzymes suitable herein include proteases such as Espe› raseR, AlcalaseR, DurazymR and SavinaseR (Novo) and Max› ataseR, MaxacalR, ProperaseR and MaxapemR (Gist-Bro› cades); and a and ~ amylases such as Purafect Ox AmR (Genencor) and TermamylR, BanR, FungamylR, DuramylR, Amylase AGR and Natalas~ (Novo); and mixtures thereof. Enzymes are preferably added herein as prills, granulates, or cogranulates at levels typically in the range from about 0.5% to about 5% pure enzyme by weight of composition. In a preferred embodiment of the present invention TermamylR is used. 

Amylases (a and/or ~) can be included for removal of carbohydrate-based residues. WO-A-94/02597 describes cleaning compositions which incorporate mutant amylases. See also WO-A-95/10603. Other amylases known for use in cleaning compositions include both a- and ~-amylases. a-Amylases are known in the art and include those disclosed in U.S. Pat. No. 5,003,257; EP-A-0252,666; WO-A-91/ 00353; FR-A-2,676,456; EP-A-0285,123; EP-A-525,610; EP-A-0368,341; and GB-A-1,296,839. Other suitable amy› lases are stability-enhanced amylases described in WO-A- 94/18314 and WO-A-96/05295 and amylase variants having additional modification in the immediate parent available from Novo NordiskA/S, disclosed in WO-A-95/10603. Also 

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