CHANGES IN IRON.

Otago Witness, Issue 1241, 11 September 1875, Page 3

CHANGES IN IRON.

In explanation of the improvement which takes place in iron, on being allowed to rest, Professor Thurston says :— There are probably two methods of improvement each due to an independent molecular action, In the cage of the, razor and 4h§

•spring, which regain their tempers when permitted to rest, it seems probable that a molecular rearrangement of the particles, disturbed by change o f temperature in the one case, and by ultimate flexing, and relaxing in the other, goes on, much as the elevation of the elastic limit, and increase of resisting power, discovered by the writer and shown on the strain diagram, takes 'place under strain and set. The oth'-r cases may probably be clue to a combination of this physical change, with another purely chemical action, which is illustrated best in the manufacture of ' steel, by the cementation process. In this process, iron, imbedded in charcoal and kept at a red heat, gradually absorbs carbon and becomes steel. Here the element carbon enters the solid masses of iron and diffuses itself with greater or, less uniformity throughout their volume.' There seems to be a tendency to uniform distribution, which is also seen in a thousand other chemical changes. Many chemical processes are accelerated, checked, and even reversed, by simple changes in the relative proportions of the elements.