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.
If, in the firing of the elements, as above set forth, all of the charcoal does not unite with the other elements, such uncombined portion should be removed from the fused mass before it is ground.
If it is designed to mix the composition with paints, those composed of zinc-white and baryta should be chosen in preference to those composed of white lead and colored by vegetable matter, as chemical action will take place between the composition and paint last mentioned, and its color will be destroyed or changed by the gradual action of the sulphureted hydrogen produced. However, by the addition of a weak solution of gum in alcohol or other suitable sizing to the composition, it may be used with paints containing elements sensitive to sulphureted hydrogen without danger of decomposing them and destroying their color.
In many, and possibly in a majority of cases, the illuminating composition applied as a dry powder will give the most satisfactory results, in view of the tendency to chemical action between the paint and composition when intimately mixed; in view of the fact that by the addition to paint of any color of a sufficient quantity of the composition to render the product luminous, the original color of the paint will be modified or destroyed; and, also, in view of the fact that the illuminating composition is so greatly in excess of the paint, the proportions in which they are united being substantially ten parts of the former to one of the latter, it will be difficult to impart a particular color to the product of the union without detracting from its luminosity. On the other hand, the union of dry powder with a body already painted by the simple force of adhesion does not establish a sufficiently intimate relation between it and the paint to cause chemical action, the application of a light coat of powder does not materially change the color of the article to which it is applied; and, further, by the use of the powder in an uncombined state its greatest illuminating effects are obtained. Again, if the appearance in the daytime of the article which it is desired to have appear luminous at night is not material, it may be left unpainted and simply sized to retain the powder.
In printing it is probable that the composition will be employed almost exclusively in the form of dry powder, as printing-ink, normally pasty, becomes too thick to be well handled when it is combined with powder in sufficient quantity to render the printed surface luminous. However, the printed surface of a freshly printed sheet may be rendered luminous by dusting the sheet with powder, which will adhere to all of the inked and may be easily shaken from the unmoistened surfaces thereof.
I am aware that monosulphide of calcium and magnesia have before been used together in phosphorescent compounds. What I claim is a phosphorescent composition consisting of monosulphide of calcium, combined with carbonate of lime, magnesia, and silex, substantially as described.
Orlando Thowless, of Newark, N.J., obtained a patent for a process of manufacturing phosphorescent substances dated November 8, 1881. The inventor says: The object of my invention is to manufacture phosphorescent materials of intense luminosity at low cost and little loss of materials.
I first take clam shells and, after cleaning, place them in a solution composed of about one part of commercial nitric acid and three parts of water, in which the shells are allowed to remain about twenty minutes. The shells are then to be well rinsed in water, placed in a crucible, and heated to a red heat for about four hours. They are then removed and placed, while still red-hot, in a saturated solution of sea salt, from which they are immediately removed and dried. After this treatment and exposure to light the shells will have a blood-red luminous appearance in the dark. The shells thus prepared are used with sulphur and the phosphide and sulphide of calcium to produce a phosphorescent composition, as follows: One hundred parts, by weight, of the shells, prepared as above, are intimately mixed with twenty parts, by weight, of sulphur. This mixture is placed in a crucible or retort and heated to a white heat for four or five hours, when it is to be removed and forty parts more of sulphur, one and one-half parts of calcium phosphide, and one-half part of chemically pure sulphide of calcium added. The mixture is then heated for about ninety minutes to an extreme white heat. When cold, and after exposure to light, this mixture will become luminous. Instead of these two ignitions, the same object may be in a measure accomplished by the addition of the full amount of sulphur with the phosphide and sulphide of calcium and raising it to a white heat but once. The calcium phosphide is prepared by igniting phosphorus in connection with newly slaked lime made chemically pure by calcination. The condition of the shells when the sulphur is added is not material; but the heat renders them porous and without moisture, so that they will absorb the salt to as great an extent as possible. Where calcined shells are mixed with solid salt, the absorbing power of the shells is greatly diminished by the necessary exposure, and there will be a lack of uniformity in the saturation. On the contrary, by plunging the red-hot shells in the saline solution the greatest uniformity is attained.
Instead of using clam shells as the base of my improved composition, I may use other forms of sea shells--such as oyster shells, etc.
I claim as new: