FertiIizers C. W. Gehrke," P. R. Rexroad, and R. A. Sweeney University of Missouri, Columbia, Mo. 6520 1
This review covers the literature reported from January 1, 1975, to December 31,1976, and includes procedures recorded in readily available journals, in Chemical Abstracts, and in Fertilizer Abstracts (37).Some selectivity has been exercised to include only those procedures especially pertinent for direct application to fertilizers, easily adapted to fertilizers, or containing information related to research in fertilizer methodology. In the Literature Cited section of this review Fertilizer Abstracts (37) are abbreviated as Fert. A.
GENERAL Reports of studies for the evaluation of various official AOAC methods for the analysis of fertilizers were summarized in a report by Rund (97).New official methods were listed, and recommendations for changes and additions to existing official methods were given. Gehrke and Rexroad (41) have reviewed the literature of analytical chemistry for 1973 and 1974 and discussed those procedures pertinent or easily adapted to the analysis of fertilizers. Procedures for N, P, K, and secondary and micronutrients were included. Halasz et al. (47)described methods developed for the rapid analysis of composite fertilizers. Phosphorus was determined by measuring the absorbance of phosphomolybdic acid under conditions where other elements forming heteropolyacids, such as silicon, did not interfere. Potassium was determined as tetraphenyl borate and the excess reagent measured by photometry in the UV range. Nitrogen, in the form of NH4+ or urea, was determined by oxidation with hypobromite and measuring the excess reagent by photometry. Procedures for plotting calibrations were also described. Bettle and Jespersen (18)noted characteristic endotherm atterns for virtually all commercial fertilizers when analyzed Ey differential thermal analysis. This relatively simple and fast method yielded qualitative and semiquantitative data amenable to identification or quality control. The simultaneous determination of N, P, and K in fertilizer and other materials was described by Andras et al. (6). The determinations were made by measurement of the intensity of y rays emitted by the sample prior to, during, and after irradiation with a neutron source of 4-MeV average energy. Jain and Sarkar ( 5 4 ) assembled a test kit consisting of a magnifying glass for assessing physical purity, along with reagents and apparatus for determining NH4+, so42-, C1-, Na+, urea, NOB-, COB^-, K+, and Ca2+in fertilizers. Radjic (93) discussed the accuracy of two methods of using a primary standard in analytical chemistry. Method I, based on a single weighing of an equivalent weight of primary standard, was compared with Method I1 in which an equivalent weight was contained in an aliquot of primary standard solution. On the basis of error in weighing and volume measurement, Method I was preferred over Method 11, especially a t high equivalent weights of primary standard. The principles and design of a high speed discrete sample analyzer were presented in a paper by Stewart e t al. (107). High flow rates were achieved without air segmentation by using small bore tubing and low sample volumes. Thus, Sampling rates of up to 120 samples/h were reported with return to baseline between samples. At this high speed, relative standard deviations of
