VGO 511: Veterinary Andrology and Reproductive Techniques (1+1)

MEASURING THE LEVEL OF LIQUID NITROGEN

• Cryogenic container should have a minimum of 15 cm level of liquid nitrogen.
• Dip stick - Used to measure the level of liquid nitrogen in cryogenic container.
• It can also be assessed by weighing the cryogenic container.

• The evaporation rate of liquid nitrogen varies between thw containers (even among same make and capacity), temperature of the room in which it is stored and number of times it is opened.
• Hence the periodic checking of the level of liquid nitrogen is essential.
• The minimum level of liquid nitrogen should keep the straws completely submerged in liquid nitrogen
  • To measure the level of LN₂, the dipstick is used
  • Open the lid, pass the stick into the container till it reaches the bottom of the container
  • Keep the stick for 10 seconds
  • Remove the stick and wave in the air for few seconds which will leads to frost formation
  • Measure the level of liquid nitrogen 1 cm below the level of frost line (this allowence is given for boiling liquid nitrogen when the stick is dipped)
  • A minimum of 15 cm should be maintained when the straws are stored in the container
• Liquid nitrogen has the specific gravity of 0.82 ie. 1 litre weighs 0.82 kg (1 kg = 1.22 litres).
• Based on the weight, the quantity of liquid nitrogen in litres could be calculated.
• For this purpose the weight of of the empty container should also be known.