Size methods soil science

Gee GW, Or D (2002) Particle-size analysis. In Dane JH, Topp GC (eds) Methods of soil analysis Part 4 physical methods. Soil Science Society of America, Madison, WL pp 255-293... 

Gee, G.W. and Or, D., Particle size analysis, in Methods of Soil Analysis, Part 4, Physical Methods, Dane, J.H. and Topp, G.C., Eds, Soil Science Society of America, Madison, WI, 2002. 

The size distribution of particles in soils and the experimental methods of obtaining them." Soil Science, 19 1-35. 

Williams, E.C. and Saunders, W.M.H. (1956b) Significance of particle-size fractions in readily soluble phosphorus extractions by the acetic, Truog, and lactate methods, youma/ of Soil Science 7, 189-202. 

Zavarzina, A. G., N. G. Vanifatova, and A. A. Stepanov. 2008. Fractionation of humic acids according to their hydrophobicity, size, and charge-dependent mobihty by the salting-out method. Eurasian Soil Science 41, no. 12 1294—1301. 

Figure 18.5. Numbered-weighted size distribution for a non-calcareous soil measured by a number of different methods (17), reproduced by permission of Soil Science Soc. of America...

The simplest method is optical microscopy, in which visible light (photons) is used to observe a sample. It has a resolution limit around 0.25-0.5 pm, which is on the order of 2/2, where 2 is the wavelength of incident light. From a strict colloid science point of view, it lies near the upper limit of colloid particle sizes and appears to be of limited utility. However, it is of great help in the identification of minerals, because it allows observation of crystal habits (the shape and size of crystals, which are determined by their internal symmetry). With experience, many minerals can be identified in a soil sample under a microscope, even from simple inspection. A unique feature of optical microscopy is the availability of polarized light, which is handy in distinguishing minerals or even different crystal types of the same compound (Bullock et al. 1985 Cady, Wilding, and Drees 2010). 

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