Boca Research None User Manual

2.3 Freeze-Pump-Thaw cycle

Using this system it is possible to operate freeze-pump-thaw cycles on sample liquids
held in any of the three vessels. Procedures appropriate to each vessel are outlined
below.

2.3.1 Sample in Vessel 1

• All taps and valves should be closed.

• Open valve V2 and tap A on Vessel 1, and freeze the sample liquid by slowly

raising a dewar of liquid nitrogen around it.

• When it has been determined that the liquid has completely frozen switch the

pump to roughing mode and open valve V1.

• Switch the pump to turbo mode and leave for several minutes. The pressure

within the system can be read from the baratron gauge on the pump.

• When sufficient pumping has been done and the sample is ready to thaw, close

valve V1 and remove the dewar of liquid nitrogen from around Vessel 1.

• The system must be ‘let-up’ to atmospheric pressure using helium gas by

opening valves V3 and V9. The pressure of gas in the system can be read
from the baratron gauge.

• Tap B should be closed to prevent suck-back of the liquid as the solid thaws.

• The sample can be warmed gently to aid the thawing process and when

complete close tap A.

2.3.2 Sample in Vessel 2

• All taps and valves should be closed.

• Open valve V2 and tap E on Vessel 2 and freeze the sample liquid by slowly

raising a dewar of liquid nitrogen around it.

• When it has been determined that the liquid has completely frozen switch the

pump to roughing mode and open valve V1.

• Switch the pump to turbo mode and leave for several minutes. The pressure

within the system can be read from the baratron gauge on the pump.

• When sufficient pumping has been done and the sample is ready to thaw, close

valve V1 and remove the dewar of liquid nitrogen from around Vessel 2.

• The system must be ‘let-up’ to atmospheric pressure using helium gas by

opening valves V3 and V9. The pressure of gas in the system can be read
from the baratron gauge.

• Valve V7 should be closed to prevent suck-back of the liquid as the solid

thaws.

• The sample can be warmed gently to aid the thawing process and when

complete close tap E.