The Romance of Modern Chemistry

HOW MAN COMPETES WITH NATURE ornamental, in the shape of emery and ruby, are very closely related. The artificial production of rubies depends simply on the careful fusion of alumina at a high temperature, and the addition of a small quantity of dichromate of potash to produce the colour. Great care must be taken in the cooling of the fused alumina ; if allowed to solidify and cool very rapidly, it is in an unstable condition, like glass which has been similarly treated. It is therefore annealed, by putting the artificial ruby while still at a high temperature in a bed of silver sand, so that the cooling takes place very slowly. Sapphires may be made in a similar fashion, except that the colouring material added is oxide of cobalt in- stead of potassium dichromate. The artificial production of sapphires, however, has not been so successful as that of rubies. A new and very striking way of making these gems has been tried lately. It has been found that when natural colourless crystals of corundum—white sapphires, as they are called—are exposed to the action of radium bromide, they undergo a gradual change of colour. Some specimens assume a blue tint, others a pink, and others still a brownish orange; so that stones of any desired tint may be obtained. In these and many other ways, then, man has been trying, and is trying, to imitate and compete with Nature. When we look back to that day in 1828 when the artificial production of carbamide was first accomplished, we are filled with wonder at the marvellous advance which has been made in the interval. Not only have we learned how to obtain artificially numbers of valuable natural products, but we can turn out of our laboratories 258