Corrosive substance due to their capabilities of dissolving greases, proteins or mineral deposits such as limescale inside water pipes. In chemical uses, high chemical reactivity is often desirable, as the rates of chemical reactions depend on the activity (effective concentration) of the reactive species. For instance, catalytic sulfuric acid is used in the alkylation process in an oil refinery: the activity of carbocations, the reactive intermediate, is higher with stronger acidity, and thus the reaction proceeds faster. Once used, corrosives are most often recycled or neutralized. However, there have been environmental problems with untreated corrosive effluents or accidental discharges. Corrosive substance A
Magic cube classes MAY be pandiagonal magic. Gardner also called this (Langman’s pandiagonal) a ‘perfect’ cube, presumably not realizing it was a higher class then Myer’s cube. See previous note re Boyer and Trump. <br>The smallest normal pandiagonal magic cube is order 7. See Pandiagonal magic cube.<br>Minimum correct summations required = 9"m" + 4. All pan-"r"-agonals sum correctly for "r" = 1 and 2. ALL 3"m" planar arrays must be pandiagonal magic squares. In addition, ALL pantriagonals must sum correctly. These two conditions combine to provide a total of 9m pandiagonal magic squares. <br>The smallest normal perfect magic cube is order 8. See