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.
The intensity of the light emitted by this composition after exposure is considerable, and largely greater than the light produced by any of the substances heretofore known.
The hereinbefore described substance may be ground with oil and used like ordinary paint; or it may be ground with any suitable varnish or be mixed in the manner of water colors; or it may be employed in any other suitable and well-known manner in which paints are employed.
My improved luminous substance is adapted for a great variety of uses--for instance, for painting business and other signs, guide boards, clock and watch dials, for making the numbers on houses and railway cars, and for painting all surfaces which are exposed periodically to direct or indirect light and desired to be easily seen during the night.
When applied with oil or varnish, my improved luminous substance can be exposed to the weather in the same manner as ordinary paint without suffering any diminution of its luminous property. I claim as my invention the herein described luminous substance, consisting of calcined chalk, sulphur, and bismuth, substantially as set forth.
Merrill B. Sherwood, Jr., of Buffalo, N. Y., obtained a patent for a phosphorescent composition, dated August 9, 1881.
The author says: My invention relates to an improvement in phosphorescent illuminants.
I have taken advantage of the peculiar property which obtains in many bodies of absorbing light during the day and emitting it during the night time.
The object of my invention is the preparation by a prescribed formula, to be hereinafter given, of a composition embodying one of the well-known phosphorescent substances above referred to, which will be applicable to many practical uses.
With this end in view my invention consists in a phosphorescent composition in which the chief illuminating element is monosulphide of calcium.
The composition obtained by the formula may be used either in a powdered condition by dusting it over articles previously coated, in whole or in part, with an adhesive substance, or it may be intimately mixed with paints, inks, or varnishes, serving as vehicles for its application, and in this way be applied to bodies to render them luminous.
The formula for obtaining the composition is as follows: To one hundred parts of unslaked lime, that obtained from calcined oyster shells producing the best results, add five parts of carbonate of magnesia and five parts of ground silex. Introduce these elements into a graphite or fire-clay crucible containing forty parts of sulphur and twenty-five parts of charcoal, raise the whole mass nearly or quite to a white heat, remove from the fire, allow it to cool slowly, and, when it is cold or sufficiently lowered in temperature to be conveniently handled, remove it from the crucible and grind it. The method of reducing the composition will depend upon the mode of its use. If it is to be applied as a loose powder by the dusting process, it should be simply ground dry; but if it is to be mixed with paint or other similar substance, it should be ground with linseed or other suitable oil. In heating the elements aforesaid, certain chemical combinations will have taken place, and monosulphide of calcium, combined with carbonate of lime, magnesia, and silex, will be the result of such ignition.