Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)


One of the most abundant and important mineral constituents of nearly all agricultural products of both animal and vegetable origin is the element calcium. When such products are ignited, the entire content of calcium remains in the ash, either in the form of oxide or combined with an acid radical, such as phosphate or sulfate. An accurate method for the estimation of calcium is of prime importance in studying the relationship between the growing plant or animal on the one hand, and the soil or food supply on the other. The separation and subsequent estimation of calcium would be comparatively simple were it not for the fact that the ash of above mentioned origin invariably contains, besides calcium, other common constituents, notably phosphoric acid, whose interference during the ordinary course of analytical procedure is so well known as to require no comment.

Having had occasion in the laboratory of the Iowa Agricultural Experiment Station to make a large number of calcium determinations in samples of forage crops and animal carcasses, the disadvantages and inconveniences of the existing methods soon became apparent. In the course of these analyses the method described in the subsequent pages of this paper suggested itself and, after being subjected to critical tests and comparisons with the method in common use, it was found to be superior both in regard to accuracy and convenience.

Before entering upon the discussion of the proposed method for determining calcium in the presence of phosphorus, a brief survey of the literature will be given.



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