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The characteristics of boron retention by layer silicates were studied. Boron retention was determined by a procedure developed for use with solution concentrations ranging from zero up to several hundred parts per million B, which consisted of treatment of the adsorbent with B solutions, washing with methanol to remove excess B, and extracting the retained B with 0.01N NaCl (pH 3).Vermiculite, kaolinite, montmorillonite, and hydrobiotite all exhibited a pH‐dependent affinity for B with maxima in the alkaline range. Access to the interlayer surfaces of the expanding lattice clays was necessary for maximum B retention by these clays. Boron retention by these layer silicates was, in the main, attributed to hydroxy iron and aluminum compounds occurring in the samples as impurities.

Colorimetric analysis of nitrate in soil extracts using chromotropic acid (CTA) was studied and compared to the results obtained by the phenoldisulfonic acid (PDA) method. Extracting solutions of 0.5M MgSO4, saturated CaSO4, and a 0.2% Ca(OH)2 suspension were investigated. The three extractants were equally effective in recovering NO3‐; however, the clearest extracts were obtained with Ca(OH)2. Soil‐to‐extractant ratios of 1:2.5, 1:5, and 1:10 were studied. The 1:5 ratio effectively extracted NO3‐ and resulted in appropriate NO3‐ concentrations for color development. A shaking time of 15 min was adequate to extract a maximum of NO3‐. In a NO3‐‐N recovery study, equivalent amounts of NO3‐ were recovered by the CTA and PDA methods. Results of nitrate analyses by the two methods were significantly correlated (p = .01). Nitrate determined by the chromotropic acid procedure was positively correlated (p = .05) with the yield of winter wheat (Triticum aestivum L.) and was negatively correlated (p = .01) with response of winter wheat to N fertilizer additions. The new procedure has the advantages of rapidity, simplicity, sensitivity, and relative freedom from interference.

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