Studies in micro-analyses

Abstract

It has been shown that the keratin tissues, hair and nails, when soaked in arsenical solution exhibit the phenomenon of preferential absorption of arsenic. The arsenic so absorbed can be partly removed by very prolonged soaking in distilled water, but rapid rinsing with either distilled water or dilute caustic soda solution. does not affect the arsenic content. By this method the maximum arsenic content of hair is found to be about 5 mgm. per 100 gm. and much higher values can be obtained in the case of nails.In vitro experiments have shown that arsenic only can travel along a hair fibre only if "creeping" of the solution along the outside of the fibre is possible.It has been demonstrated that arsenic absorbed into hair in vivo cannot be removed by prolonged soaking, and this fact is tentatively put forward as the basis of a method of distinguishing between arsenic absorbed in vivo and arsenic resulting from external contamination.Details of the method of destroying organic matter previous to analysis, and the accuracy of the Marsh test using the electrolytic process, are also discussed.