Apparently excess exposure to oxygen isn't a terribly big factor or it wouldn't be used. You have at least two options if you are concerned about excess exposure.
1) Use an inert gas to top off with after stirring.
2)
<DIV ="colorSub">Cool Stir Large Volume Magnetic Stirrer
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Large Volume Stirring Simplified!
The improved Cool Stir® Large Volume Magnetic Stirrer safely and effectively mixes liquid volumes from 10 liters up to 208 liters (2.5 to 55 gallons) using inert PTFE magnetic stirring bars. An internal high strength aluminum frame and large chemical resistant polypropylene platform are built to safely support up to 220kg (485lbs) allowing stirring in a standard plastic drum. The 39 x 39cm (15 1/2 x 15 1/2") footprint is small enough for benchtop use with containers up to 80 liters (20 gallons). A direct drive motor rotates a powerful rare earth driving magnet that couples optimally with 76 through 160mm (3" through 6") stirring bars typically used to stir in large vessels. Mixing speed is infinitely variable to approximately 600 rpm (maximum practical rpm dependent on volume and viscosity) for gentle stirring up to aggressive agitation with full depth vortex. All electronic controls and the 100 watt (1/8 horsepower) motor are air cooled and insulated to prevent any heat transfer to valuable solutions. Sturdy polypropylene side panels are easy to clean in case of spills and protect users from all moving parts.
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<TH noWrap>SKU </TH>
<TH>Description </TH>
<TH style="TEXT-ALIGN: center">Units </TH>
<TH style="TEXT-ALIGN: right">Price </TH>
<TH style="TEXT-ALIGN: center; e98b03: " width=120>Quantity </TH></TR>
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<TD noWrap>60-370280001 </TD>
<TD width="50%">Cool Stir Large Volume Magnetic Stirrer, 80 Liters </TD>
<TD align=middle>1 </TD>
<TD align=right>$2128.00 </TD>
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I think the first option would be cheaper.</>
Edited by: appleman