and includes procedures recorded in readily available journals, in Chemical A bstracts, and in Analytical A . Some selectivity has been exercised to include only those procedures especially pertinent or those which in the authors' judgement, could be adapted easily to fertilizer analytical problems. SAMPLINGThe results of a survey regarding the specifications and details of sampling bagged fertilizers was reported by Gehrke (30). Adherence to the recommended equipment and procedures of the AOAC was quite good. No serious sampling problems were reported. The recommended bag sampler specifications, detailed in the study, based on the most widely used equipment were adopted as official first action by the Association of Official Analytical Chemists. (22) found the results of a preliminary collaborative study of Karl Fischer titration methods for the determination of free and total water in fertilizers to be in wide disagreement. It was recommended that the proposed methods of the AOAC be rewritten in explicit detail. WATER DuncanA study was also made by Duncan to determine the effect of grinding during preparation for analysis on the moisture content of triple superphosphate (23). The findings indicated that there was some correlation between relative humidity and absorption of water when a sample of granular triple superphosphate was ground in preparation for analysis. It was suggested that care be exercised in the preparation of superphosphate samples for analysis and the relative humidity in the grinding room probably should be 140%.A collaborative study was made by Duncan (24) of the 1,4-dioxane extraction method for free water and the distillation method for total water in fertilizer. The extraction method for free water compared favorably with the official vacuum desiccation method and was adopted as an official first action method by the AOAC. However, nitrate interfered with the proposed method for total water; therefore, study of the total water method was discontinued. NITROGENAn automated spectrophotometric method, utilizing Technicon AutoAnalyzer modules, to determine total nitrogen in fertilizers containing only ammoniacal, nitrate, and urea nitrogen has been developed by Gehrke et al. (31). This colorimetric system employs the Berthelot ammonia-phenate-hypochlorite reaction. A homogeneous chromous/titanous reduction system for the automatic reduction of nitrates has been interfaced with the digestion phase and color development manifold, resulting in a totally automated system for determining nitrogen in fertilizers with an effective analysis rate of 20-25 samples p e~ hour. A newly developed sample-retrieval system removes digested samples from the helix. In comparing data for 458 samples analyzed by the Missouri Automated Nitrogen Method (MANM) and the C o r prehensive Nitrogen Method (CNM), 2.053-2.054, the aTrerage difference between the two methods (MANM-CNM) was +0.04% nitrogen. The average relative difference was 1.12%. The average value for 140 samples of KNO3 primary standard analyzed by the ...
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