Humic and hymatomelanic acids isolated from five different soils of varying organic matter contents were subjected to electrometric titrations. The electrometric studies, namely, those of interaction of the different humus fractions with bases and neutral salts, are clearly indicative of the polyelectrolytic behaviour of these high molecular acidic components. The similarity of the behaviour of natural humic acids with hymatomelanic acids was clearly noticeable, suggesting the genetic similarity between them.