THE ROYAL MUMMIES. 'of nitrogen peroxide with the colouring matter. The com-,pound formed is insoluble in water. It has been urged that the natural bleaching of flour by storage is a process similar ;to that which takes place in the bleaching plant, the only "difference being that artificial bleaching effects in the course of a few seconds what would, under ordinary circumstances, require one or two months for completion. In other words, ,the same ultimate result is attained whether the flour

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... ,bleached rapidly by the use of comparatively large quantities of nitrogen peroxide, or slowly by the gradual absorption of nitrogen peroxide from the atmosphere. Subsequent ,experiments showed that the colour of carrotene may be discharged either by the oxygen of the air or by nitrogen peroxide, the processes, however, being quite 'distinct and resulting in the formation of different 'substances. Thus, pure carrotene on exposure to air is bleached by absorption of oxygen, but no oxides of nitrogen are absorbed from the air. The inference is that the natural ageing of flour is a similar process, and that .in the bleaching of flour by nitrogen peroxide certain .substances are :produced which are not produced during the natural ageing of flour. The attempt, therefore, to justify bleaching flour with nitrogen peroxide on the ground that it is merely copying, but hastening, a natural ,process of bleaching (i.e., by ageing) must fail.