American cinematographer (Jan-Dec 1924)

December, 1924 AMERICAN CINEMATOGRAPHER Seventeen How About Oskaloosa, Iowa? How will your photography impress the patrons of the Gem Theatre? The answer is simple if you know that the print was made from A PRACTICAL NEGATIVE — a negative carefully and honestly treated for artistic printing BEYOND THE DAILYS — a negative so good that it forbids uneven printing — — a negative which reflects creditably in a "key" theatre or in a small house on the 57th booking — // this means anything to you — there's but one answer! ROTHACKER-ALLER LABORATORIES, Inc. 5515 Melrose Ave. HOLLYWOOD, CALIFORNIA HOIlywood 7 1 80 (a) Experiments with Yeast. In the experiments with yeast about lcc. of ordinary baker's fresh yeast was placed in a 250cc bottle of the solution to be tested. When yeast was added to a 1% solution of sodium thiosulphate a considerable yield of sulphide was obtained in less than 24 hours. With a 1 % solution of sodium sulphite, sulphide was detected after four or five days. When MQ tank developer was diluted 1 to 3, and 0.25% hypo added with yeast, sulphide was invariably produced in 3 to 5 days. Finally, when yeast alone was added to a slightly used tank developer, and the bottle kept closed for a week, sulphide was detected in considerable concentration. Thus there is no doubt whatever that ordinary baker's yeast contains organisms which are capable of living in a developer and producing sulphide from the developer constituents. (b) Experiments with Slime. The wooden wash tanks in which the motion picture film is washed after fixing becomes coated with a thin layer of slime if they are not cleaned frequently. Some of the slime was scraped off and kept in a bottle from which portions were taken and added to other solutions. The bottle containing slime was partly filled with water from the tap and after keeping a few days a lead acetate paper blackened instantly when introduced into the top of the bottle. In this case the sulphide must have been produced from traces of sulphate in the tap water, or hypo from the water in the wash tank from which the slime was scraped. Sulphate was formed very slowly and in small amounts when slime was added to hypo solutions or to dilute developers containing hypo. However, when some of the slime was added to slightly used developer and the bottle kept tightly closed for two weeks, a large amount of sulphide was formed. Therefore, the slime which collected on the walls of the wash tanks was capable of producing sulphide in a developer. (c) Bacteriological Examination of the Developer. A sample of the fogging developer from the tank after standing for some time was examined microscopically* and found to contain numerous organisms, some of which were undoubtedly dead. The turbidity of the contaminated samples appeared to be caused largely by the suspended organisms. A second sample obtained from the tank just as the first trace of fog became evident showed much the same bacterial flora as the first. This consisted chiefly of bacteria, bacilli predominating, although cocci were present. Under anaerobic conditions in a medium of diluted developer to which peptone and lead acetate had been added hydrogen sulphide was produced on at least three occasions. It is not certain yet which one of the mixtures of micro-organisms yielded the hydrogen sulphide nor can the peptone be ruled out as the source of it. In view of all the experimental evidence produced, it seems certain that the sulphide in the fogging developers tested was formed from sulphite as the result of reduction by living organisms which grew in the developer. The organisms were probably introduced with the water, but may have come from the air. A deep tank favors such growth because oxygen cannot penetrate to the bottom of *The authors are indebted to Dr. R. R. Mellon and Dr. W. S. Hastings of the Pathological Laboratory, Highland Hospital, Rochester, New York for the bacteriological examination.