On the perchlorate method for the estimation of potassium in soils, fertilisers, etc.

Abstract

(1) It is shown that the presence of chloric acid in the perchloric acid used for the estimation of potassium in soils, fertilisers, and plant material, by Davis's method (l) gives rise to very erratic and erroneous results. Every sample of perchloric acid should, therefore, be tested for freedom from chloric acid before being used for the estimation of potassium.(2) Results are quoted which indicate that in the application of Neubauer's method of treatment of the soil extract to a soil deficient in carbonates, it is sufficient to add only 0·1 gm. of calcium carbonate to the extract instead of the 0·5 gm. generally used. A considerable economy of perchloric acid is thereby effected.