The advantages of the invention consist in obtaining for the purposes of daily life a light which is maintained at no cost whatever, is free from the defects and contingent dangers arising from combustion or heat, and can be applied in many cases where all other sources of light would be inconvenient or incapable of application.
Heretofore phosphorus has been mixed with earthy oxides, carbonates, and sulphates, and with oxides and carbonates of metal, as tin, zinc, magnesia, antimony, and chlorides of the same, also crystallized acids and salts and mineral substances, and same have been inclosed and exhibited in closely-stopped bottles as a phosphorus; but such union I do not claim; but what I claim is:
A luminous paint, the body of which is a phosphorescent substance, or composed in part of such substance, the vehicle of which is such as is ordinarily used in paints, viz., one which will become dry by oxidation or evaporation, substantially as herein described.
A. Krause, of Buffalo, N.Y., obtained a patent for improvement in phosphorescent substances dated December 30, 1879. The patentee says: This invention relates to a substance which, by exposure to direct or indirect sun-light, or to artificial light, is so affected or brought into such a peculiar condition that it will emit rays of light or become luminous in the dark.
It is a well-known fact that various bodies and compositions of matter, more especially compositions containing sulphur in combination with earthy salts, possess the property of emitting rays of light in the dark after having been exposed to sun-light. All of these bodies and compositions of matter are, however, not well adapted for practical purposes, because the light emitted by them is either too feeble to be of any practicable utility, or because the luminous condition is not of sufficient duration, or because the substances are decomposed by exposure to the atmosphere.
Among the materials which have been employed with the best results for producing these luminous compositions are sea-shells, especially oyster-shells. I have found by practical experiments that only the inner surface of these shells is of considerable value in the production of luminous compositions, while the body of the shell, although substantially of the same chemical composition, does not, to any appreciable extent, aid in producing the desired result. It follows from this observation that the smallest shells, which contain the largest surface as compared with their cubic contents, will be best adapted for this purpose.
I have found that chalk, which is composed of the shells of microscopic animals, possesses the desired property in the highest degree; and my invention consists, therefore, of a luminous substance composed of such chalk, sulphur, and bismuth, as will be hereinafter fully set forth.
In preparing my improved composition I take cleaned or precipitated chalk, and subject it to the process of calcination in a suitable crucible over a clear coal or charcoal fire for three or four hours, or thereabout. I then add to the calcined chalk about one-third of its weight of sulphur, and heat the mixture for from forty-five to ninety minutes, or thereabout. A small quantity of bismuth, in the proportion of about one per cent, or less of the mixture, is added together with the sulphur.
The metal may be introduced in the metallic form in the shape of fillings, or in the form of a carbonate, sulphuret, sulphate, or sulphide, or oxide, as may be most convenient.
The substance produced in this manner possesses the property of emitting light in the dark in a very high degree. An exposure to light of very short duration, sometimes but for a moment, will cause the substance to become luminous and to remain in this luminous condition, under favorable circumstances, for upward of twenty-four hours.