Fig. 6.—Scholl's Platinum Light Perfecter.

Scholl's "Platinum Light Perfecter." An ingenious device for improving the efficiency of union-jet burners was brought out some twenty years ago by a Mr. Scholl, of London, and known as Scholl's "Platinum Light Perfecter," which is shown in the accompanying illustration. It consisted of a little brass ring, carrying a plate of platinum about 0·4 inch long by 0·15 inch wide. The ring fitted on to the top of the burner in such a manner that the platinum plate was held, in a vertical position, between the two orifices from which the gas emerged. The jets of gas, instead of impinging upon each other, impinged against the plate, and united above to form the flame. By the interposition of the metal plate, the velocity of the gas was much reduced; and a thicker and more sluggish flame was produced, with the result of increasing its illuminating power. When the apparatus was used upon a burner having very small orifices, and delivering its gas at a high pressure, the increase of light obtained was very striking; but with lower pressures the advantage derived from its use was correspondingly diminished. This is very clearly shown by the following table, which is extracted from a report, by Captain Webber and Mr. Rowden, on experiments upon gas-burners, carried out at the Paris Universal Exhibition, 1867.[ [4]

Illuminating Power.
Kind of Burner.Cubic Feet
of Gas
per Hour.		Pressure
in
Inches.		Without
Perfecter.		With
Perfecter.		Increase
per
Cent.
Leoni's fishtail, No. 230·841·34·1215
Leoni's fishtail, No. 330·462·44·691
40·702·86·5132
Leoni's fishtail, No. 440·474·57·668
50·715·09·284
Leoni's fishtail, No. 540·425·36·930
50·606·18·336
60·817·110·040[5]
Leoni's fishtail, No. 640·316·28·029[6]
50·468·010·430[7]

Burners were also made with the metal plate forming part of the burner head; and, instead of being of platinum, it was sometimes formed of thin steel, or other commoner metal. Where platinum was used, some advantage probably accrued from its becoming incandescent; but, of course, any benefit arising from this source was not obtained when steel was employed. The remarks which have been made respecting the limited applicability of the double-flame burner will apply, with equal force, to the apparatus under notice. Although it effected an undoubted improvement when applied to burners ill adapted to the pressure at which the gas was supplied, equally good results could be obtained without its aid, when a burner was employed suited to the quality and pressure of the gas supplied.

Leoni's flat-flame burners. Perhaps the most efficient flat-flame burners available prior to 1867 were those made by Mr. S. Leoni, of London. One of these is shown in fig. 7. This maker produced both batswing and union-jets; various sizes being made of each burner. Besides affording fairly good results from the gas consumed, the burners were supplied at a very moderate price. Their distinguishing feature was the peculiar substance of which the burner-tips were formed. This was a material invented by Mr. Leoni, and named by him "adamas." (The precise composition of "adamas" is a trade secret; but it appears to consist of a mixture of various minerals or earths, moulded in a clayey or plastic condition, and then burnt.) Previous to his invention, the tip of the burner, or the burner head, had been made, almost exclusively, of iron or brass. There were, however, some grave defects inherent in the use of metal for this purpose. The orifices of union-jets and the slits of batswings in course of time became much obstructed by the corrosion of the metal; and the efforts made to remove the obstruction only served to destroy the burner more quickly, by increasing the size and injuring the precise shape of the apertures. The "adamas" tips, on the other hand, perfectly withstood the high temperature to which they were exposed, were quite incorrodible, and were sufficiently hard to endure a considerable degree of even rough usage. By constructing the tip of this material, the efficiency of the burner was improved in many ways. The liability of the burner to corrosion being removed, and the inconvenience due to this cause done away with, the life of the burner was prolonged, and the expense of renewal consequently reduced. But, in addition to these advantages, there was yet another direction in which the "adamas" tip contributed to enhance the utility of the burner. This was in maintaining a higher temperature of the flame; and arose from its inferior capacity, compared with metal, for conducting heat from the flame. That the advantage derived from this source, although unimportant, was not altogether imaginary, will be apparent when it is mentioned that metal burners, when in operation, usually attain to a temperature of from 400° to 500° Fahr.—an indication of the amount of heat being continuously abstracted from the flame. The adoption of a non-conducting material for the burner-tip, while it did not entirely prevent, considerably reduced the loss of heat.

Fig. 7.—Leoni's Flat-Flame Burner.

Two varieties of each class of burner were made by Mr. Leoni. In the one burner, the "adamas" tip was inserted into an iron stem; in the other, the tip was inserted in a brass body, which fitted on to the iron stem. Between the brass body and the iron stem of the latter burner there was affixed a layer of wool, designed to check the pressure at which the gas was supplied. Owing, very probably, to the unsuitability of the material (wool) used for this purpose, the result was not satisfactory; as, according to the statements of Messrs. Webber and Rowden, in the report previously cited, no difference could be detected, in many experiments, between the results yielded by the burner with or without the layer of wool. Some light is shed upon this apparent anomaly by certain experiments made by the writer to determine the pressure at which gas issues from various burners. With one of Leoni's No. 4 union-jets, under an initial pressure of 1 inch (the pressure at the inlet when the burner is in operation), the pressure at the outlet of the burner, when the layer of wool was employed, was 0·11 inch; but from the same burner, when the layer of wool was removed, the gas issued at a pressure of only 0·07 inch. Thus the effect of inserting the layer of wool in the burner was exactly the opposite of that which it was intended to produce; the pressure of the issuing gas stream being increased instead of diminished.