A separation of microscopic particles from sea water

The seawater sample is filtered through a glass-fiber filter or a membrane filter previously treated with a little fine magnesium carbonate powder to prevent particles adhering to the surface of the membrane. If necessary the particulate matter may be rinsed off the membrane filter prior to analysis by using a jet of filtered sea water. 

The filtration gear has been discussed in the section notes on apparatus. 

It is convenient to arrange matters so that 2- to 5-liter bottles holding the samples are clamped in an inverted position in the Millipore filter funnels. Filtration can then proceed unattended. 

Methods for the adequate sampling of the euphotic zone are outside the scope of the present procedure. The final sample or subsample for analysis should be passed through nylon netting as a precaution to remove any large animals or con- 

Use freshly filtered water from the first sample being analyzed in each batch. Do not store. 

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