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The photographic news
- Bandzählung
- 7.1863
- Erscheinungsdatum
- 1863
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- SLUB Dresden
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- Public Domain Mark 1.0
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- http://digital.slub-dresden.de/id1780948042-18630000
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- oai:de:slub-dresden:db:id-1780948042-18630000
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- LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
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- Parlamentsperiode
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- Bandzählung
- No. 245, May 15, 1863
- Digitalisat
- SLUB Dresden
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Zeitschrift
The photographic news
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Band
Band 7.1863
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- Register Index 619
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Band
Band 7.1863
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- Titel
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THE PHOTOGRAPHIC NEWS. 231 Fixing Solution. Cyanide ... 10 grs. Water 1 on. Nitrate silver ... 1gr. Wash thoroughly. If not sufficiently dense, use— Iodine resublimed ... ... ... 2 gr. Iodide potassium ... ... ... 1, Citric acid ... ... ... ... 1, Water 1 oz. Be sure and not make up this solution with alcohol, as it causes stains on the plate. My friend, Mr. Blanchard, in a late article, states that he has found that by the use of the iodine the negatives become hard. They do so without the citric acid, but I have printed fully 2,000 prints from one negative, intensified with my formula, and the last was equally as good in tone as the first. The addition of the nitric acid is also important, the plate works foggy and dirty without it—with it, clean and brilliant—the difference would be found at once. It also enables the iron solution to be kept for along time without deteriorating. Wash well and use Pyro... I} grs. (hot weather) 2 to 3 „ (cold weather) Citric acid 1} „ Water 1 oz. Add 2 drops of a 20-grain solution of silver, not from the bath. Keep this moving on the plate until the solution becomes of a pale sherry colour, or rather, to the inexpe rienced operator, until the points of light appear sparkling and brilliant. Then well wash. It must be apparent to every one that citric acid in this formula is brought prominently forward; for many years it has been my constant habit of using it. I found when Using the collodions of Bolton and Co., Thomas, and Perry (Sheffield), that it gave me brilliant and beautiful negatives "'hen others who used acetic acid failed. Mr. Keene, of Leamington, recommends acetic and citric acids mixed in the pyro solution; this gives very excellent results, but it Occasions a little extra washing ; it however rather tends to keep the positive soft and harmonious. In conclusion, should any of your readers bo tempted, in the course of the summer, to visit Boss and the lovely scenery of tire Wye, I shall be happy to see them and help them out of any difficulties they may get into, photographical of course. Scitentitir Gossiy. sis, after having passed through the pre- of wonder and implicit credence, has now arrived at that point at which people begin to throw doubts "pon the absolute accuracy of its deductions. It has been lately discovered that the spectrum of an clement is not always identical in its different compounds; lines which arc absent in one compound being rendered apparent by the presence of another body, and strong definite lines, hitherto considered to be characteristic of an element, being alto gether effaced when some other body is present. M. Mitscherlich has remarked that the spectrum given by chloride of barium in presence of an excess of hydrochloric Aid, is quite different to the spectrum of barium itself At first he was inclined to attribute this fact to the presence o another metal, and in order to satisfy himself on this Point he examined it synthetically. The arrangements su opted were very simple; the solutions to be examined were p aced in a glass tube, closed at the upper end, and having Tb oer. i rawn to a point and bent nearly to aright angle. 10 flowed slowly through a bundle of fine platinum nJ' 5 01 ged in the point, and allowing at the same time immJ" of air into the tube. He usually added a salt of 1 o the solutions to facilitate the volatilisation of Spectrum analy liminary gtAceg the dissolved salt. In studying the chloride of barium spectrum he filled one of these tubes with a solution of acetate of baryta, with the addition of acetate of ammonia, and he filled another tube with concentrated hydrochloric acid. Upon placing the extremity of the first tube in a flame he found it produced rays characteristic of barium. When this was removed, and the tube containing hydro chloric acid was placed in the flame, no lines whatever were produced; but on placing the bundles of platinum wires at the extremity of these two tubes simultaneously in the flame, he saw the spectrum which he had previously obtained with chloride of barium. M. Mitscherlich has noticed analogous facts with the chlorides of calcium and strontium : but upon experimenting with iodides, fluorides, and sulphides of the alkaline earths, similar results were not obtained, the spectra observed being those character istics of the metals themselves. Copper gave curious results in its different combinations ; the chlorides and iodides of copper give distinct spectra according to the combination. Sulphide of copper gives no spectrum; this fact might bo attributed to the fixity of this combination, but the following experiment puts this explanation out of the question :— A solution of chloride of potassium, in presence of sal ammoniac and excess of hydrochloric acid gives no spectrum in spite of the volatility of chloride of potassium, whilst this salt by itself, and much more diluted, gives the charac teristic ray of potassium. This may be accounted for by the reduction of the salt being in the latter instance effected by the flame, which in the first instance could not bo the case. It is important to note the fact that certain rays in the spectrum of a metal may be effaced by the presence of a different substance in the flame: thus, the blue ray of chloride of strontium disappears in presence of the spectrum produced by chloride of copper with addition of sal ammoniac. Wishing to go a step further M. Mitscherlich sought to discover whether the rays usually considered characteristic of metals were produced by the metal itself as by its oxide. For this purpose it was necessary to avoid the reducing action of the flame. With this object he heated the combi nation to redness in a porcelain tube closed at each end with glass; and commenced by receiving on the spectro scope the light emanating from the inside of the tube con taining the combination partially reduced to vapour. This light being very feeble he placed a bright flame at tho other extremity of the heated tube, allowing thus the rays furnished by the substance to be observable owing to their being reversed. M. Mitscherlich’s experiments were chiefly with soda, sodium, chloride of sodium and carbonate of soda ; sodium alone gave a spectrum under these circum stances. With all deference to the opinion of M. Mitscher lich, who is well known as an accurate and acute observer, we do not agree with the conclusions he draws from these experiments. He says that the result of these researches is that to the free metal alone are due its characteristic rays, and that if they are seen with its combinations, reduction takes place by the carbon and hydrogen of the flame. Very possibly this may be the case, indeed some recent researches about which we shall have more to say shortly, seem to prove that it is so, but we cannot admit that M. Mitscher lich’s experiments prove anything except that the heat to which he submitted his porcelain tube was not sufficient to volatilize the contained soda salts. Sodium was the only substance which gave a spectrum under these circumstances, because it was the only body which could be volatilized at the temperature employed. To render the experiment worth anything the heat should have been raised suffi ciently to render the other soda salts thoroughly gaseous, and then if their vapours, seen through the length of the tube, were unable to plough out the black line D from the continuous spectrum of the luminous flame, it might’, be regarded as evidence of what is attempted to be proved; but as the experiment at present stands it merely
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