Dried fruits and nuts were fumigated with a mixture of propylene oxide (PPO) and CO2 (8%:92% w/w) in 28.42-litre chambers to determine PPO sorption rates in these products and toxicity to a variety of postharvest insect pests. A 48-h fumigation using a rate of 45 mg/litre at 38°C resulted in more than 97% sorption in almonds, pecans and walnuts, and induced 100% mortality of mixed life stages of the following insects: Indian meal moth (Plodia interpunctella), red flour beetle (Tribolium castaneum), confused flour beetle (T. confusum), warehouse beetle (Trogoderma variabile), cigarette beetle (Lasioderma serricorne), lesser grain borer (Rhyzopertha dominica) and saw-toothed grain beetle (Oryzaephilus surinamensis). The 48-h fumigations resulted in PPO residues in the nuts that were below the tolerance level (300 ppm). The residues dropped to undetectable levels following aeration for 3 days. A 24-h fumigation of walnuts, raisins and figs infested with P. interpunctella, Trogoderma variabile and dried fruit beetle (Carpophilus hemipterus) using a rate of 75 mg/litre at 26.7°C resulted in 78, 95 and 93% sorption, respectively, but failed to provide complete mortality of the insects. Susceptibility to PPO was C. hemipterus > P. interpunctella > T. variabile. The rate of PPO sorption into walnuts, raisins and figs was independent of rate.

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Gilsonite pitch and polyvinyl chloride (PVC) were carbonised at slow rates of 0 . 5 "~ min-I and the products of carbonisation examined by chromatography, mass spectrometry, nuclear magnetic resonance spectroscopy, optical microscopy, scanning electron microscopy and electron spin resonance spectroscopy. The original Gilsonite pitch contains -5 % of aromatic protons, rising to 24 % in soluble material just prior to formation of the graphitisable semi-coke at 410"~. The carbonised PVC melts ( 3 8 9 "~) to form a black isotropic liquid with 23 % aromatic protons, rising to 41 % at the onset of the coalescence of the mesophase spheres ( 4 2 0 4 4 0 "~) .The constituent molecules are considered to be hydrogenated cyclic structures possessing a great variety of saturated and unsaturated side-groups . During carbonisation, there is loss of side-groups, but it is the essentially aliphatic cyclic structures which co-cdense to form the mesophase. Further aromatisation must occur within the mesophase and semi-coke. The presence of heteroatoms within the Gilsonite pitch is considered to restrict the Rrowth of the mesophase structures and their ability to coalesce to form the much larger units of anisotropic character observed in the case of PVC. Electron spin resonance spectroscopy suggests that free radicals are not necessary to form the mesophase, the free radical character being developed afrer formation of the mesophase, probably as the aromaticity is developed.

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