American cinematographer (Jan-Dec 1924)

Sixteen AMERICAN CINEMATOGRAPHER December, 1924 INVESTIGATIONS ON PHOTOGRAPHIC DEVELOPERS (Continued from page 9) film are passed repeatedly through the developer, fixing bath, and wash tanks, it is possible that traces of hypo might be carried into the developer as a result of incomplete washing of the racks. With this in mind a small wooden frame was soaked in a fixing bath, and without rinsing was dried for two days, and then soaked in a liter of developer in a small tank for three days. This developer was then tested and found to give some dichroic fog which has a different appearance from fog caused by sulphide. Moreover, no sulphide could be detected by chemical tests. When hypo in increasing amounts was added directly to a fresh developer, the general result was to decrease the density of the image without producing any increase in fog. Dichroic fog was formed in only a few cases. From these tests it seems improbable that traces of hypo in a developer can form sulphide by chemical decomposition. 2. Rubber. Rubber bands are used to fasten the ends of strips of film to the racks for tank development, and in the tube machine mentioned a soft rubber washer and hard rubber base were in contact with the developer. Therefore, a handful of new rubber bands were placed in a 250cc. bottle of developer and allowed to stand 24 hours at a temperature of 120°F. Another sample of developer was heated to boiling with rubber bands. In both these tests no excessive fog was produced and sulphide could not be detected. When rubber was heated with 10% sodium hydroxide alone, sodium sulphide was formed, but when heated with sodium hydroxide and sodium sulphite, hypo was formed instead of sulphide. The same result was obtained with developer which contained sulphite. 3. Free Sulphur. Flowers of sulphur were added to a developer and tested, as with the rubber bands, by boiling and by keeping for 24 hours at 120°F. Solutions were then filtered and tested chemically and photographically but no sulphide could be detected. However, so much hypo was formed that, after a strip of film had been developed in the solution kept for 24 hours at 120°F., a silver mirror was slowly formed on the walls of the glass tube containing the developer. This was due to reduction of the silver dissolved from the emulsion. The solution also had a muddy appearance from the precipitated silver. Similar tests were carried out with milk sulphur made by acidifying a hypo solution. In all these tests the results were the same ; no sulphide was formed in a developer by adding hypo, rubber which contains sulphur, or free sulphur. On the other hand, when free sulphur was added to a developer, either hypo or some other poly-thio salt which dissolves silver bromide, was formed. 4. Decomposition of Gelatine. When film is passed through a developer a small amount of gelatine dissolves in the solution. Ordinary gelatine may contain cystine as one of its constituent amino acids and cystine contains sulphur in organic combination. Moreover, cystine is quite soluble in alkalies. It was thought therefore, that if the gelatine in the emulsions contained traces of cystine this might get into the Neuberg and Welde, Transformation of Thiosulphate into Hydrogen Sulphite by Yeast, Bio-chem. Z 67, 111, 1914). Fred W. Tanner, Formation of Hydrogen Sulphide from Certain Sulphur Compounds by Yeast-like Fungi. Am. Chem. Soc. 40,663, (1918). W. J. Wilson, Reduction of Sulphites by Certain Bacteria and Media Containing a Fermentable Carbohydrate and Metallic Salts. J. Hyg, 21, 392, (1923). Kilpatrick and Kilpatrick, The Stability of Sodium Thiosulphate Solutions. J. Am. Chem. Soc. 45, 2132, (1923). developer and be decomposed with the formation of sulphides. In order to test this possibility some pure cystine was added to a developer, both alone and with ordinary gelatine, and the solutions kept for several days at 120°F. The same test was also made at 90°F. No sulphide was detected in any of these solutions. It is known that the bacterial fermentation of protein bodies containing sulphur produces hydrogen sulphide and in these tests it is probable that conditions favorable to bacterial development were not present, although the solutions were inocculated from the fogging developer. Moreover, it seems improbable that sufficient cystine could get into a developer from photographic gelatine to account for the formation of sulphide in the concentrations found to exist. In considering the activities of bacteria and other organisms, however, a much more probable source of the sulphide was found. V. The Reduction of Sodium Thiosulphate, Sulphite, and Sulphate by Bacteria, Moulds and Yeasts 1. Literature. The literature contains references to the reduction of thiosulphates, sulphites, and sulphates by many different organisms. Neuberg and Welde' found that with a mixture of sodium thiosulphate, sugar and yeast, hydrogen sulphide and sodium sulphite were formed, and in three days 15% of the theoretical yield of hydrogen sulphide was obtained. Tanner2 studied the action of thirty different fungi and found that most of the strains liberated hydrogen sulphide from sodium thiosulphate. Ten were found to reduce sodium sulphate to hydrogen sulphide and a few reduced sodium sulphite. W. J. Wilson3 found that in media containing sodium sulphite, glucose and iron salts, reducion of sulphite to sulphide is effected by B. typhosus, B. enteritidis, B. paratyphosus B., and other members of the Salmonela group. These examples are sufficient to indicate the great variety of organisms which are capable of reducing sulphites, or even sulphates to hydrogen sulphide. It is also of interest to note that a rapid deterioration of standard solutions of thiosulphate has been traced to bacterial action4. 2. Experimental Investigation. In order to confirm the theory that reducing organisms were responsible for the formation of hydrogen sulphide in the fogging of developer, it was necessary to reproduce the effect in other samples of developer. For most tests the solution to be tested was placed in a 250cc. bottle, the desired culture material added, and the sample kept in an oven at 90 — 95°F. The bottles were not quite full and were corked. In some cases the solution itself was tested, but generally a lead acetate paper was suspended in the top of the bottle and left for an hour or two, if necessary, to see if it would blacken. At first some of the tests gave negative results, but this was probably due to the fact that the bottles were opened too frequently for examination and, as will be shown later, the absence of oxygen is a contributing factor in the formation of sulphide.