Centrifuge assembly used in this method is that described by Gillman (1976) (Figure 14.3). This design may be adapted to fit the cup size of any medium size laboratory centrifuge (3–5 L capacity).
Figure 14.3 Centrifuge assembly of Gillman (1976) used to obtain soil SEs.
Prepare SE as detailed in Method 14A1. Transfer aliquot (usually 250 g) of paste to a stainless steel cylinder (Figure 14.3) on top of a Whatman No. 40 filter paper and cover with polyethylene film.
Assemble apparatus in centrifuge cup, balance the load, then centrifuge at a RCF of ≈900 for ≈15 min. Always adhere to the centrifuge manufacturer’s instructions (see Notes 1 and 2 of Method 14A3). After centrifugation, pass any SEs not totally clear through a 0.20 μm Millipore filter, prior to preparation for analysis and reporting, as detailed in Method 14A1 and later in this chapter.