KBS006: Gillson Pneumatic Elutriator


Setting up the elutriator

Turn on air until the needle reads across from the black 20. Turn
on water to 70 psi. Both these gauges should be checked regularly;
during elutriation water should be at 30-40 psi.

Processing samples

Before pouring the soil into the chamber, break up all large
clumps of soil and turn on the chamber to allow it to fill halfway
with water. Add sample, making sure sieve system is in correct order
of (from top to bottom) 710, 425, and 243 at the bottom. Elutriate
0-5 cm samples for 10 minutes and 5-15 samples for 15 minutes. When
the sample is done, remove all connecting chamber and sieve systems
and rinse through into sieves to make sure nothing is left in the
arm. As you take apart the system of sieves and connectors, rinse
through each part into the next sieve down. Empty chamber and turn
on, allowing it to rinse out for a few seconds.

Filtering samples

243 sieves should always be placed in the large funnels to be
rinsed out. For 0-5 cm samples, the 425 and 710 sieves can be placed
in smaller funnels unless the sample is unusually large. For 5-15 cm
samples, the 425 is placed in a large funnel and the 710 is placed
in a small funnel. It helps to wet the filter paper before placing
the sieve in the funnel. Rinse off the outside of the sieve and
rinse through screen, brushing lightly wit the tip of the water
bottle to knock off material that is sticking. Use a spatula to
remove all seeds that remain on the inside of the sieve after
rinsing. The filter paper is easiest to remove from the funnel with
the pump still on. If seeds have slipped down underneath the filter
paper, rinse out of funnel onto filter paper. Place filter paper in
appropriately labeled petri dish, not fully covering so that the
filter paper will not dry and seeds will not germinate. When the
filter paper is dry, cover the petri dish and tape securely for


Label petri dishes and filter paper ahead of each sample.

Use white grease to keep sieves and connectors from sticking
together. Avoid getting grease in the mesh on the sieves because it
will cause seeds to stick and water to back up.

Make sure the chamber you are using has three functioning air jets.

The pump should read at 200 or above on the red scale when it is
functioning properly. If this is not the case, there could be
several causes:1) all connections with hoses should be tight; 2) the
rubber stoppers should be pressed into the beakers as tightly as
they can be; 3) the switch on the funnel should be in the vertical
position when that funnel is on; 4) try to limit the number of
funnels you have on at any one time; 5) make sure no water can get
into the pump by emptying the beaker out frequently.


in progress