The Optical Magic Lantern Journal (December 1889)

The Optical Magic Lantern Journal and Photographic Enlarger. 53 Flashes on Lantern Topics. BRIN’s OXYGEN Process.—It is a rather remarkable fact that the principle underlying this method of abstracting the oxygen from the atmosphere was fully stated, and its value appreciated, many years before the present easy method had been arrived at. In the edition of Professor Roscoe’s Chemistry for 1874 (Macmillan) it is mentioned, and shortly stated it is this:—'' When baryta is gently heated ina current of oxygen gas, the two substances combine to form a dioxide, containing twice as much oxygen as baryta ; this additional atom of oxygen is however evolved at a higher temperature, and it has been proposed to use this decomposition for the manufacture of oxygen from the air. For this purpose, as soon as the dioxide Ba O2 has been reduced to Ba O, the temperature is lowered and air passed over the baryta ; this, again, takes up oxygen passing into Ba 02, which again is decomposed at a higher temperature. This interesting process has, however, been found not to work in practice.” In Brin’s method it has been found practicable to such an extent that the operation may be repeated as many as one hundred and fifty times in the course of a day, thus reducing the cost of the production of oxygen to that of the fuel, labour, and the wear and tear of the necessary plant. The heat required for the purpose is stated roughly at 1,400 degrees. I notice also that by a further improvement in the process of manufacture, the decided impurity of the earlier samples has now been quite eliminated, and a nearly pure oxygen gas can be supplied at a very low price. which ought to be good news for lantern workers. The impurity alluded to was simply admixtures of : atmospheric air, diluting and reducing the quality of the pure gas, which is the result of the beautiful expe fifteen years ago. How many years earlier it might have been known, or was on record, I am not certain, but I know it was one of the laboratory experiments, and formed one of the instructive themes of the late Professor Samuel Brown, of Edinburgh, but he, unfortunately for science, died quite young, before the world had got its full value out of the man who was admiringly ! called by his friends Te Napoleon of Chemistry. Professor Penny, of Glasgow, also used the same experiment in his lectures in the Andersonian University Chemistry Class there about the years 1852--6, which T can well remember, as it was there I saw the first photographic transparencies I had then seen shown by the optical lantern. The demonstrator was Dr. Taylor, in the Natural History Class, and the fact may well be here recorded. A description of the primitive appliances of that lantern would seem very laughable now, but the effects were wonderfully good. : getting the anzesthetic ether 1 When you force gas The transparencies were, if not the same size, yet very nearly the same as we now use. The subjects were views taken in rambles round the picturesque environs of Glasgow, and were from wet collodion negatives, and they were also made by the same process. In.memory I often turn my mental bull's-eye on those very beautiful pictures, as they were among the first of my introductions to the practical working of our art-recorder—photography. BULL’S-EYE. ——_+ Ether Saturators, and Lime-Light Matters. Tue Rev. J. FREDERICK HARDWICH, in a communication to us says :—“ It has occurred to me that the enclosed correspondence between myself and an old lanternist of thirty years standing may interest your readers.” “Dear Sir,—Excuse the liberty which I take, knowing the great interest you have long shown in lantern matters. I am a user of the ethoxo light, and last night was very much bothered with roaring of the jet. I should be much obliged if you would inform me whether you find a large or small nozzle the best with ether, to obtain a maximum of light. The exhibition lasted nearly two hours, and I found, on weighing the saturator, that exactly 4 02. of ether (717) had been used. I cannot say how much oxygen, as I have not gauged the bottle, which had a pressure of 1,000lb. on the inch at the sta:t. Of course I use a regulator, which works very satisfactorily. I want to get the best light possible, and don't wish to save a trifle in oxygen and ether. A friend told me he always gets the best light with a roaring jet, but the noise is very unpleasant, to say the least of it. “T like the saturator very well. This is the third season I have used it, and with suitable ether find no trouble. I had a curious experience last winter. The winter before I bought a Winchester quart of ether; I forget the gravity, but it was not so good as the ‘717 I now use It worked all right : : : | during that season, but last winter it caused small explosions riment so clearly described and published by Roscoe, in the tube, and though the flannels of the saturator were dried, it made no difference. I could only conclude the lighter part of the ether had been used at first. Since (-717) 1 have had no hitch at all except this noise. —Yours faithfully,” &c. Rev. T. Frederick Hardwich’s reply. “ Dear Sir,—! Roaring of the jet’ is usually caused by working at ‘too high pressure. Much, however, depends upon the proportions of the two gases, because when the ether is in excess, and the flame red at the tip and edges, double the pressure can often be used without producing ‘ roaring. In order to cure it, turn off the oxygen tap of the jet slowly until the noise ceases, and turn it on again just short of the point at which the roaring begins. . “The aperture of the jet need not be very Jarge in the case of ether, because the oxy-ether is a more spreading flame than the oxy-hydrogen, and heats a larger surface of the lime; one twenty-Afth of an inch will be enough. There is, however, an advantage in working with an aperture of onetwentieth of an inch, when economy is not an object, for noises of all kinds are less frequent with large apertures. through a very narrow tube, whistling, humming, buzzing. and roaring are all liable to happen. “ After all is said, much depends upon the jet being carefully