potassium chlorite for chlorates sodium chlorate potassium chlorate and ammonium chlorate for perchlorates sodium perchlorate ammonium perchlorate and potassium perchlorate for iodates sodium iodate ammonium iodate and potassium iodate for hypochlorites sodium hypochlorite potassium hypochlorite and calcium hypochlorite for nitrites sodium nitrite potassium nitrite and ammonium nitrite for bromates potassium bromate sodium bromate and ammonium bromate for peroxyphosphates potassium peroxydiphosphate sodium peroxydiphosphate and ammonium peroxydiphosphate for nitrates sodium nitrate potassium nitrate and ammonium nitrate mercury salts of the above are unsuitable because of ecological considerations one or more of the oxidizing agents may be used at the same time in addition to the above solid compounds oxygen and chlorine dioxide gases are suitable in the practice of my invention air is a very inefficient source of oxygen i have also found that oxygen can be generated in the etching bath by making the aluminum work piece the anode the cathode must be a separate compartment since the evolved hydrogen and oxygen must be separated in the practice of my invention the alkali metal etching bath is either continually or periodically treated with one of the above oxidizing agents to maintain a small concentration of oxidizing agent from about 0 0001 to about 1 gram per liter of etchant solution a preferred concentration range of oxidant is from about 0 01 to about 0 1 gram liter of etchant solution at higher concentrations the oxidizing agents produce an architectural type of finish on the aluminum the solid oxidizing agents can be added to the etching bath either as a powder or in aqueous.