Suche löschen...
The photographic news
- Bandzählung
- 35.1891
- Erscheinungsdatum
- 1891
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- SLUB Dresden
- Lizenz-/Rechtehinweis
- Public Domain Mark 1.0
- URN
- urn:nbn:de:bsz:14-db-id1780948042-189100009
- PURL
- http://digital.slub-dresden.de/id1780948042-18910000
- OAI
- oai:de:slub-dresden:db:id-1780948042-18910000
- Sammlungen
- Fotografie
- LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
- Strukturtyp
- Band
- Parlamentsperiode
- -
- Wahlperiode
- -
- Bandzählung
- No. 1722, September 4, 1891
- Digitalisat
- SLUB Dresden
- Strukturtyp
- Ausgabe
- Parlamentsperiode
- -
- Wahlperiode
- -
-
Zeitschrift
The photographic news
-
Band
Band 35.1891
-
- Ausgabe Ausgabe 1
- Ausgabe Ausgabe 17
- Ausgabe Ausgabe 37
- Ausgabe Ausgabe 57
- Ausgabe Ausgabe 77
- Ausgabe Ausgabe 97
- Ausgabe Ausgabe 117
- Ausgabe Ausgabe 137
- Ausgabe Ausgabe 157
- Ausgabe Ausgabe 177
- Ausgabe Ausgabe 197
- Ausgabe Ausgabe 217
- Ausgabe Ausgabe 237
- Ausgabe Ausgabe 257
- Ausgabe Ausgabe 277
- Ausgabe Ausgabe -
- Ausgabe Ausgabe 313
- Ausgabe Ausgabe 329
- Ausgabe Ausgabe 345
- Ausgabe Ausgabe 361
- Ausgabe Ausgabe 377
- Ausgabe Ausgabe 393
- Ausgabe Ausgabe 409
- Ausgabe Ausgabe 425
- Ausgabe Ausgabe 441
- Ausgabe Ausgabe 457
- Ausgabe Ausgabe 473
- Ausgabe Ausgabe 489
- Ausgabe Ausgabe 505
- Ausgabe Ausgabe 521
- Ausgabe Ausgabe 537
- Ausgabe Ausgabe 553
- Ausgabe Ausgabe 569
- Ausgabe Ausgabe 585
- Ausgabe Ausgabe 601
- Ausgabe Ausgabe 617
- Ausgabe Ausgabe 633
- Ausgabe Ausgabe 649
- Ausgabe Ausgabe 665
- Ausgabe Ausgabe 681
- Ausgabe Ausgabe 697
- Ausgabe Ausgabe 713
- Ausgabe Ausgabe 729
- Ausgabe Ausgabe 745
- Ausgabe Ausgabe 761
- Ausgabe Ausgabe 777
- Ausgabe Ausgabe 793
- Ausgabe Ausgabe 809
- Ausgabe Ausgabe 825
- Ausgabe Ausgabe 841
- Ausgabe Ausgabe 857
- Ausgabe Ausgabe 873
-
Band
Band 35.1891
-
- Titel
- The photographic news
- Autor
- Links
- Downloads
- Einzelseite als Bild herunterladen (JPG)
-
Volltext Seite (XML)
626 THE PHOTOGRAPHIC NEWS. [September 4, 1891. THE DECOMPOSITION OF SILVER CHLORIDE BY LIGHT * BY A. RICHARDSON, PH.D. Examination of the Darkened Chloride for Oxyyen.—The question whether the darkened compound is an oxy chloride or a subchloride of silver appeared to be best decided by a careful examination of the compound for oxygen. The first experiments made in this direction consisted in heating the dry, darkened product in a vacuum, and collecting any gas which might be given off. 26 grams of pure silver chloride, which had been exposed to light under water until it had lost 8 per cent, of its total chlorine, was dried at 110°, and placed in a hard glass tube closed at one end, and connected at the other with a Sprengel pump ; after the tube was exhausted, a graduated tube containing mercury was inverted over the turned-up end of the fall tube of the pump, in order to collect any gas which might be given off on heating. On gently warming the tube containing the chloride, it was found that just at first small quantities of gas were carried over ; when gas ceased to come off, the temperature was raised and kept at the melting point of the chloride for about half an hour, during which period no further gas was evolved. The total volume of gas collected = 0'6 c.c.; this was proved to be air contained in the powder and on the glass, for, on shaking with alkaline pyrogallol, only a minute contraction of about 0’1 c.c. took place. In a second experiment, 20 grams of the darkened chloride, from which 7 per cent, of the total chlorine had been removed by exposure to light, was heated as in the previous experiment; in this case, also, a minute quantity of gas was given off, which measured 0’4 c.c. at 0° and 760 mm. It appears from these results that if oxygen is present in combination with the darkened chloride, it is not given off at the melting point of the silver chloride with which it is associated. The next experiments were made to determine whether water was formed when the darkened product was heated in pure hydrogen. The gas, which was prepared by the action of steam on metallic sodium, was first dried by passing it through tubes containing sulphuric acid, then led over metallic copper heated to redness, and, finally, the last traces of moisture were removed by means of phosphorus pentoxide. The gas so obtained was passed into a combustion tube, in which the darkened chloride was to be heated. This tube was drawn out at one end and terminated inside a bulb, which was connected with a weighed phosphorus pentoxide tube, the escaping gas then passing through a second drying tube, and finally into a bulb containing water, in which the hydrochloric acid was absorbed. That phosphorus pentoxide does not absorb dry hydro gen chloride to any appreciable extent (when exposed to the gas for a few hours only) was proved by the fact that the gain in weight of such a drying tube, after being ex posed to the action of hydrogen chloride for 3} hours, was only 0 003 gram, and that, on again passing the gas for two hours, no further increase in weight could be de tected.! Tubes which had been exposed to the action of the gas till the weight remained constant were used in the subsequent experiments. Before heating the darkened silver chloride in hydrogen, the combustion tube was ex hausted and gently heated until the air adhering to the * Continued from page 605. + Dry air was drawn through the tubes before weighing. _ glass and pulverised chloride had been removed ; the tube was then heated in the current of hydrogen, the tem perature being gradually raised till the chloride began to show signs of fusing. It was important, however, that the temperature should not rise too high, as the hydrogen chloride formed was found to act on the glass, carrying over small quantities of calcium chloride, which possibly (in one case) reached the weighed phosphorus pentoxide tube. The reduction, which lasted from seven to eight hours, was found to be complete when the escaping gas failed to give any turbidity with silver nitrate. The results are given of four experiments made in the manner described. In the first three the darkened chloride was obtained from silver chloride from which 8 per cent, of chlorine had been removed by the action of light. In the last experiment, pure silver chloride was reduced in order to determine how far the gain in weight in the phosphorus pentoxide tube was due to experimental error. In the second experiment the tube had been strongly heated, and it was most probable that a trace of calcium chloride was carried over. Table V. Weight of darkened chloride taken. (1) 24'64 grams (2) 22'35 „ (3) 24-24 „ (4) 13’0 , (normal chloride) Gain in weight of P,O, tube. 0'00375 gram 0'00475 „ (very strongly heated) 0'00325 gram 0'00250 ,, From these experiments, it will be seen that the increase in weight in the phosphorus pentoxide tubes is so small as to preclude the possibility of the presence of an oxygen compound of silver in the darkened chloride. In conclusion, it may be mentioned that, as a further proof of the absence of oxygen in this substance, an ex periment, which is a modification of one described by Carey Lea (Amer. J. Sci. 38, 356-361), was made. Silver chloride was dried with extreme care and placed in a tube containing pure, dry carbon tetrachloride, from which all air was expelled by boiling. On exposure to light the chloride rapidly darkened, although it was certain that no oxygen was present. Chamois Skins.—Considering what a useful thing a chamois skin is. it is astonishing that there is so much ignorance as to the proper way of keeping it in order and lengthening its term of service. Chamois skins should never be left in water after being used, but should be wrung out and hung up to dry, being spread out carefully so as to leave no wrinkles. They should not be used to wipe off colours, as paint stains form hard spots, and make the skin wear out sooner. Chamois was never intended to wipe the face and hands with, which makes the skin become greasy. Never put a chamois skin into warm water ; anything above lukewarm water will curl it up, making it become thick, tough, and useless. To bring back chamois that has been injured by grease and paint, or used as a towel until it resembles a dirty old rag, the following is recommended : Take a bucket of clean water which has been made fairly but not too strong with ammonia ; soak the skin in it over night, and the next morning rinse it out in pure water, after which use pure white Castile soap and water freely. The whole operation, aside from the soaking, need take no longer than a quarter of an hour, and it makes the skin in reality better than it was before, having freed it from all impurities.—The Optician. The September- issue of Die Photographic, in an appreciative notice, announces the death of Emanuel Mariot (Schielhabl), at the age of sixty-six.
- Aktuelle Seite (TXT)
- METS Datei (XML)
- IIIF Manifest (JSON)