Method for controlling the proportion of fluid passing through a filter

A method for dividing a fluid containing material dissolved or suspended therein into desired proportions, said method comprising the steps of:

• (a) providing at least one filtration device, said filtration device comprising a filter;
• (b) adding said fluid to said at least one filtration device;
• (c) placing said at least one filtration device to which said fluid has been added in a pressure vessel, said pressure vessel capable of withstanding a specified level of pressure relative to ambient pressure;
• (d) sealing said at least one filtration device to form a trapped volume downstream of said filter, said trapped volume being hermetically sealed from air space in remainder of said pressure vessel, whereby mass of air in said trapped volume is sealed against escape or entry of air;
• (e) increasing the pressure in said pressure vessel upstream of said filter;
• (f) allowing a period of time to elapse, said period of time being sufficient to allow said fluid to flow through said filter into said trapped volume, whereby the pressure downstream of said filter in said trapped volume is allowed to reach a level that is substantially equal to the pressure upstream of said filter, whereby a desired proportion of said fluid passes through said filter;
• (f) unsealing said at least one filtration device;
• and
• (g) venting said pressure vessel.