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66. The effect of irradiation on the keeping quality of fish
282
Abstracts of Papers
observed. The initial radiation yields of all products were markedly greater using pile radiation. These yields increased more rapidly with rise in temperature than did those obtained with electron irradiation. T h e concept that equal energy inputs from differing types of radiation cause equal damage does not seem to hold for this class of compound. 4. The thermal decomposition of para-terphenyl and Santowax-K has been studied at temperatures of 420 to 470°C. Observations on the effect of certain metals on the decomposition of Santowax-R, and of its compatibility with these metals, will be described. 5. The effects of increasing degrees of irradiation on the thermal and flow properties of para-terphenyl and Santowax-R were determined over a wide range of temperature. Typical data will be presented.
P/63. T h e Effect o f Ionlzhag R a d i a t i o n on Solid Catalysts. E.J. GIBSON, R. W. CLARKE, T. A. DOrtLXNG and D. Pope (United Kingdom). 1. One of the more attractive ways in which ionizing radiations might be used in chemical industry is for the treatment of solid catalysts. I f a single moderate dose of radiation can be made to produce a change in the,catalyst which results in a long-lived enhancement in catalytic activity, or an improvement in selectivity, then a significant reduction in catalyst cost per unit of product might be achieved. 2. Oxides would appear to be the most promising catalysts for an initial study of this possibility, and this paper presents some results obtained during a study of the irradiation of iron oxide catalysts with the g a m m a radiation from cobalt-60. T h e main interest has been in the use of these catalysts for reactions involving carbon monoxide and hydrogen. 3. It has been found that after a dose of g a m m a radiation of the order of 1 to 5 × 107 rep, some iron oxide catalysts show a long lived increase in activity for the synthesis of hydrocarbons from carbon monoxide and hydrogen at 280°G and 10 to 20 atmospheres pressure. The increased activity persists to the end of the tests, some of which lasted 300 hours. T h e product obtained using the irradiated catalyst did not differ significantly from that obtained using the untreated catalyst. 4. However, not all iron oxide catalysts for this reaction can be affected in this way, and some differences between the catalysts are discussed. 5. Measurements of electrical conductivity, oxo-electron emission and other properties have been carried out on some of the catalysts tested, and the information so far obtained is discussed in relation to the catalytic activity of the samples.
P/66. T h e Effect o f Irradiation on the K e e p i n g Q n a l i t y o f F i s h . J. M. SHEWAN and J. LISTON (United Kingdom). I. Results are discussed of two recent experiments designed to test the usefulness ofirradlation in fish preservation. In the first, in which a 4 M e V cathode ray apparatus was used, a variety of species, haddock, cod, ling, lemon sole, mackerel and herring including kippers, was treated at
doses from 0"25 to 3.5 million rads and the effect on the sensory characteristics of the fish assessed by a trained taste panel. It was concluded that low dose levels were the most suitable for fish, cod and lemon sole being the least affected. 2. In the second experiment, only cod fillets packed in polythene bags were used, these being irradiated, with a cobalt-50 source of g a m m a rays, at levels of 0-25, 0.5, and 1.0 million rads. One additional batch of fillets, irradiated at 0'25 million rads, was dipped in 20 p.p.m of chlortetracycline for 30 minutes prior to irradiation. Control and irradiated fillets were stored at both 0 ° and 15°C and samples examined by the sensory, chemical and bacteriological methods usually employed to follow the spoilage changes in stored fish. 3. T h e most significant feature of the results was the enhanced effect produced by the combined antibiotic and irradiation treatments. Thus after 2 days at 15°C only the latter fish were acceptable to the taste panel; while at 0°C the controls were approaching inedibility 9 days after irradiation, and those subjected to 0"25, 0.5 and 1.0 million rads by the 13th day. The irradiated, antibiotic dipped fish, on the other hand, were still edible on the 23rd day. There seemed, +however, to be little correlation between these sensory changes and the chemical data (the amounts of total volatile bases and trimethylamine in the flesh). The numbers of bacteria on the surfaces of the fish were at first considerably reduced by irradiation. After two days at 15°C however, the counts were as high in the irradiated fish as in the controls, only the antibiotic-irradiated samples remaining low. Similar results were obtained at 0°C. Thus both initially and during storage the controls had counts of about 10~ to 107 per sq. cm of surface. The irradiated samples at the beginning of storage had values of less than l0 s per sq. era, but these increased during the 23 day storage period to about l0 s per sq. cm while the samples subjected to both irradiation and the antibiotic never exceeded 10 s. Qualitative analyses of the flora showed that irradiation produced a marked reduction in the Pseudomonas types present and since these are believed to be mainly responsible for spoilage it is perhaps not surprising that the combination of antibiotic and irradiation should result in such enhanced keeping quality.
P1127. Steel C o r r o s i o n ha the P r e s e n c e o f I-]hS. J. J. P o i n t (Belgium). The presence of H2S accelerates the corrosion of steel. According to some authors, this is due to hydrogen induced embrittlement. The details of the corrosion process are not known, however, and the behaviour o f some steels, as regards HgS corrosion, is different from what it is with respect to hydrogen. According to some authors, the possible diffusion of sulphur between the joints of the grain (which is made apparent in some specific instances), is the main phenomenon. Since the situation was rather confused, the author resorted to tracers in order to clarify the mode o f action of HsS. H e used S as (for a study of the internal and superficial distribution of the sulphur) and radioactive cations (for the purpose of localizing the cathodes and
Abstracts of Papers
observed. The initial radiation yields of all products were markedly greater using pile radiation. These yields increased more rapidly with rise in temperature than did those obtained with electron irradiation. T h e concept that equal energy inputs from differing types of radiation cause equal damage does not seem to hold for this class of compound. 4. The thermal decomposition of para-terphenyl and Santowax-K has been studied at temperatures of 420 to 470°C. Observations on the effect of certain metals on the decomposition of Santowax-R, and of its compatibility with these metals, will be described. 5. The effects of increasing degrees of irradiation on the thermal and flow properties of para-terphenyl and Santowax-R were determined over a wide range of temperature. Typical data will be presented.
P/63. T h e Effect o f Ionlzhag R a d i a t i o n on Solid Catalysts. E.J. GIBSON, R. W. CLARKE, T. A. DOrtLXNG and D. Pope (United Kingdom). 1. One of the more attractive ways in which ionizing radiations might be used in chemical industry is for the treatment of solid catalysts. I f a single moderate dose of radiation can be made to produce a change in the,catalyst which results in a long-lived enhancement in catalytic activity, or an improvement in selectivity, then a significant reduction in catalyst cost per unit of product might be achieved. 2. Oxides would appear to be the most promising catalysts for an initial study of this possibility, and this paper presents some results obtained during a study of the irradiation of iron oxide catalysts with the g a m m a radiation from cobalt-60. T h e main interest has been in the use of these catalysts for reactions involving carbon monoxide and hydrogen. 3. It has been found that after a dose of g a m m a radiation of the order of 1 to 5 × 107 rep, some iron oxide catalysts show a long lived increase in activity for the synthesis of hydrocarbons from carbon monoxide and hydrogen at 280°G and 10 to 20 atmospheres pressure. The increased activity persists to the end of the tests, some of which lasted 300 hours. T h e product obtained using the irradiated catalyst did not differ significantly from that obtained using the untreated catalyst. 4. However, not all iron oxide catalysts for this reaction can be affected in this way, and some differences between the catalysts are discussed. 5. Measurements of electrical conductivity, oxo-electron emission and other properties have been carried out on some of the catalysts tested, and the information so far obtained is discussed in relation to the catalytic activity of the samples.
P/66. T h e Effect o f Irradiation on the K e e p i n g Q n a l i t y o f F i s h . J. M. SHEWAN and J. LISTON (United Kingdom). I. Results are discussed of two recent experiments designed to test the usefulness ofirradlation in fish preservation. In the first, in which a 4 M e V cathode ray apparatus was used, a variety of species, haddock, cod, ling, lemon sole, mackerel and herring including kippers, was treated at
doses from 0"25 to 3.5 million rads and the effect on the sensory characteristics of the fish assessed by a trained taste panel. It was concluded that low dose levels were the most suitable for fish, cod and lemon sole being the least affected. 2. In the second experiment, only cod fillets packed in polythene bags were used, these being irradiated, with a cobalt-50 source of g a m m a rays, at levels of 0-25, 0.5, and 1.0 million rads. One additional batch of fillets, irradiated at 0'25 million rads, was dipped in 20 p.p.m of chlortetracycline for 30 minutes prior to irradiation. Control and irradiated fillets were stored at both 0 ° and 15°C and samples examined by the sensory, chemical and bacteriological methods usually employed to follow the spoilage changes in stored fish. 3. T h e most significant feature of the results was the enhanced effect produced by the combined antibiotic and irradiation treatments. Thus after 2 days at 15°C only the latter fish were acceptable to the taste panel; while at 0°C the controls were approaching inedibility 9 days after irradiation, and those subjected to 0"25, 0.5 and 1.0 million rads by the 13th day. The irradiated, antibiotic dipped fish, on the other hand, were still edible on the 23rd day. There seemed, +however, to be little correlation between these sensory changes and the chemical data (the amounts of total volatile bases and trimethylamine in the flesh). The numbers of bacteria on the surfaces of the fish were at first considerably reduced by irradiation. After two days at 15°C however, the counts were as high in the irradiated fish as in the controls, only the antibiotic-irradiated samples remaining low. Similar results were obtained at 0°C. Thus both initially and during storage the controls had counts of about 10~ to 107 per sq. cm of surface. The irradiated samples at the beginning of storage had values of less than l0 s per sq. era, but these increased during the 23 day storage period to about l0 s per sq. cm while the samples subjected to both irradiation and the antibiotic never exceeded 10 s. Qualitative analyses of the flora showed that irradiation produced a marked reduction in the Pseudomonas types present and since these are believed to be mainly responsible for spoilage it is perhaps not surprising that the combination of antibiotic and irradiation should result in such enhanced keeping quality.
P1127. Steel C o r r o s i o n ha the P r e s e n c e o f I-]hS. J. J. P o i n t (Belgium). The presence of H2S accelerates the corrosion of steel. According to some authors, this is due to hydrogen induced embrittlement. The details of the corrosion process are not known, however, and the behaviour o f some steels, as regards HgS corrosion, is different from what it is with respect to hydrogen. According to some authors, the possible diffusion of sulphur between the joints of the grain (which is made apparent in some specific instances), is the main phenomenon. Since the situation was rather confused, the author resorted to tracers in order to clarify the mode o f action of HsS. H e used S as (for a study of the internal and superficial distribution of the sulphur) and radioactive cations (for the purpose of localizing the cathodes and