Arsenic is one of the metals found in cured tobacco and mainstream cigarette smoke. Levels of arsenic in modern filtered cigarette smoke range from sub-ppm to a few tens of ppms. To enable accurate smoke toxicity assessment on arsenic in cigarette smoke, it is desirable to establish its chemical forms in addition to total quantities because different arsenic compounds possess different toxicological potentials.Progress has been made on measuring the arsenic speciation in tobacco and mainstream cigarette smoke by using a combination of synchrotron-based X-ray absorption spectroscopy and high-performance liquid chromatography- inductively coupled plasma mass spectrometry (HPLC-ICP-MS). In this paper, we describe the experimental procedures developed together with the main findings. A transient redox transformation between As(V) and As(III) was confirmed in freshly generated mainstream smoke. Potential areas for future research are highlighted in order to further our understanding of the speciation mechanism for arsenic in tobacco products.

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1. Considerable differences were found in the specific conductivities of different soils at any one time of the year, and considerable differences in any one soil at different times of the year, the specific conductivities being highest in March and lowest in June and July. Hence it is only possible to compare different soils when samples of these soils are taken at the same time of the year.2. A relation has been found between the specific conductivities of the soil extracts and the mean weights of lint per plant per row in the case of 2 strains of Ishan cotton. Other data are presented showing that the specific conductivity of a 1 to 5 soil extract is an index of the fertility of the soil.3. It has been found that the specific conductivity of a soil decreases under continuous cultivation. There is evidence that the rate of solution also decreases under the same condition.

Measurements have been made of the electrical conductivity of aqueous suspensions of stored soil samples taken at intervals of several years from four of the Rothamsted classical plots bearing the same crop every year. The results show that under continuous cropping:1. The initial conductivity (and therefore the soluble salt content) of an unmanured soil decreases steadily to a minimum value, which then remains fairly constant over a long period of years. There is reason to believe that, under the same conditions, the normal initial conductivity of a continuously manured plot (excluding the temporary increased measurements due to application of manure) decreases similarly to a fairly constant minimum value, which is slightly greater than that of an adjacent unmanured soil depending on the kind and probably on the quantity of manure applied.2. The 7 days’ increase of both unmanured and manured soil decreases progressively. In the case of an unmanured soil for which earlier samples were available, the 7 days’ increase is found to decrease comparatively rapidly during the first few years of continuous cropping.