Grain surface

The grain surface or specific surface (= surface area per unit weight) increases very sharply in batches of grain with decreasing mean grain diameter. In soil science and sedimentology , the grain size distribution plays an important role, because many properties of soils (more precisely the soil type ) and sediments depend on this composition; The grain surface is a measure of the expected water binding or ion exchange.

Because the grain diameter ranges are very large, they are measured at intervals of powers of ten with the factors 2 and 6.3, with 6.3 dividing the range between 2 and 20 on the logarithmic scale into equal sections.

The table gives the surface and the volume of the spherical individual grains as well as the number of these individual grains, which have a total volume of 1 cm³, for the limits of grain diameter ranges that are customary in soil science and sedimentology. Assuming a uniform density of 2.6 g / cm³, the number of grains per gram and the specific surface area are listed in m² / g.

Table: Surface, volume and specific surface
for different grain diameters at a density of 2.6 g / cm³

Diameter mm	Surface mm²	Volume mm³	Number per cm³ 1 / cm³	Number per g 1 / g	Surface area per g m² / g
2.0000	12,566371	4.1887902048	239	92	0.00116
0.6300	1.246898	0.1309243030	7638	2938	0.00366
0.2000	0.125664	0.0041887902	238732	91820	0.01154
0.0630	0.012469	0.0001309243	7638001	2937693	0.03663
0.0200	0.001257	0.0000041888	238732415	91820160	0.11542
0.0063	0.000125	0.0000001309	7638001324	2937692817	0.36721
0.0020	0.000013	0.0000000042	238732414638	91820159476	1.19366
${\displaystyle d=2r}$ ${\displaystyle r={\text{Radius}}}$	${\displaystyle O=4\pi r^{2}}$	${\displaystyle V={\frac {4}{3}}\pi r^{3}}$	${\displaystyle N={\frac {(10\,{\text{mm}})^{3}}{V[{\text{mm}}]}}}$	${\displaystyle {\frac {N}{2,6}}}$	${\displaystyle {\frac {O[{\text{mm}}^{2}]}{1000^{2}}}\cdot {\frac {N}{2,6}}}$

See also

• Grain size

swell

• Winfried EH Blum: Soil science in brief . Bornträger, Berlin, Stuttgart, 2007, ISBN 3-443-03117-X
• Karl Heinrich Hartge: Introduction to Soil Physics . Schweizerbart'sche Verlagbuchhandlung, 1999, ISBN 3-510-65223-1