Fumigation of agricultural products. V.—The distribution of nicotine vapour in glasshouses

Abstract

The extension of the bromothymol-blue method to the determination of nicotine vapour in glasshouses is described. The vapour pressure of technical nicotine is discussed, and the factors that influence the distribution of nicotine vapour in glasshouses are assessed.Glasshouses are so leaky that effective fumigation ends when the nicotine has been ebaporated. 0 2 . per 1000 cu. f t . and the rate of evaporation should be about 4 oz. per hour for each of the usual spirit-lamp evaporators. Fumigation should not be done while the temperature is rising because marked layering of the atmosphere is liable to occur. Stirring, in conjunction with the leaky structure, only enhances loss of fumigant.The optimum dosage is about Strong cross-winds are likewise deleterious. IntroductionThe general methods of following the distribution of fumigants in ships, warehouses and special chambers have been extensively investigated and described.' Much less has been published about glasshouse fumigation, although the distribution of nicotine and methyl bromide in glasshouses has been given a preliminaryThe leakage from glasshouses is so much faster than that from even the most makeshift fumigation chamber that it becomes the dominant feature of the fumigation, and makes the sorption of fumigant, which is an important source of loss in most fumigations, less significant.found that insect control was better a t higher temperatures, that winds caused uneven distribution in the glasshouse, and that high humidities had little apparent effect on the toxicity of the methyl bromide used as a fumigant in one of the only two sets of experiments reported. There was some sealing of the soil when this became wet, and soil penetration was then reduced. When nicotine concentrations were measured in large glasshouses, it was found that the concentrations fell to negligible proportions within an hour of beginning the fumigation.2 Better results were obtained in dry rather than wet conditions.