Sulphuric acid—continued leaching

Rubisov, D. H. Papangelakis, V. G. Sulphuric acid pressure leaching of laterites—a comprehensive model of a continuous autoclave. Hydrometallurgy 2000, 58, 89-101. 

We believe the discrepancy is due to the following points which are not taken into account in these various formulas. First, if we assume we have a continuous agitation system made up of four agitators, in which we are leaching pyrites cinders with 10 per cent sulphuric acid the system will become balanced and the strength of the sulphuric acid in the four tanks will become constant. For purposes of comparison, we will assume this to be ... 

First, there would appear to be an apparent discrepancy in the fact that since 1974 acidity of rain in these areas has not increased (indeed sulphur emissions in Western Europe have fallen), but the trend to loss in fish populations in Scandinavia and Scotland has on the whole continued. This, on the face of it, can be explained by a continued leaching out of base cations and loss of buffering capacity from the top soils through which most of the run-off occurs, and the slow response time of fish populations in lakes to loss of spawning trout in tributory streams. However, at the same time an explanation must also be found for the following ... 

Zinc is prepared electroanalytically from an acid solution of purified zinc sulphate, using aluminium sheets as cathodes and anodes of pure lead. The anodic reaction is the liberation of oxygen, and so the concentration of free sulphuric acid tends to increase continuously to counter this the electrolyte is circulated, and the more acid solutions are returned to the leaching process. 

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