Cupric Chlorite

Copper (II) Chlorite. See Cupric Chlorite under Chlorites in this Vol... 

The primary function of the mammalian red blood cell is to maintain aerobic metabolism while the iron atom of the heme molecule is in the ferrous (Fe+2) oxidation state however, copper is necessary for this process to occur (USEPA 1980). Excess copper within the cell oxidizes the ferrous iron to the ferric (Fe+3) state. This molecule, known as methemoglobin, is unable to bind oxygen or carbon dioxide and is not dissociable (Langlois and Calabrese 1992). Simultaneous exposure of sheep to mixtures of cupric acetate, sodium chlorite, and sodium nitrite produced a dose-dependent increase in methemoglobin formation (Calabrese et al. 1992 Langlois and Calabrese 1992). 

Catalysis of these reactions has been reported . At pH 3.5, cupric ion is said to catalyse the process (1) and ferric ion, the process (2). The latter appears to be third order in chlorite. Nickel and cobalt salts had less selective action. The first-order reactions reported by Ishi involve rate coefficients comparable to those above and thus the orders may be wrong. The maximum yield of CIO2 near pH 2, which was found by Buser and Hanisch , has been confirmed . A low order (1.69) in chlorate was found with acetate buffers and may be explained by the above mechanism. Further studies in this pH region are required, but it is likely that the process initiated by (11) is predominant, and produces CIO2 more rapidly than either (3) or (10) . 

A number of etchants are in use, depending upon the nature of the process and, to an extent, peisona] preferenoe or tradition. These include (1) afnmORium persulphate (2) sodium persulphate (3) potassium peroxysulphate (4) cupric chloride (5) FeClj (6) HjCrO (7) ammoniiN at chlorite and (8) hydrogen... 

Modern ammoniacal etchants are mildly alkaline solutions containing ammonium carbonate, cupric and chlorite ions together with proprietary additives. Metallic etch resists including tin-lead are not usually attacked but the pH and solution composition must be maintained in order to preserve the etch rate and prevent sludge formation. A possible set of reactions is ... 

Certain ammoniacal solutions are operated without chlorite ions, dissolved oxygen maintaining the dissolved copper in the cupric state ... 

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