Veterinary Andrology and Reproductive Techniques

Assessment of LN2 level

ASSESSMENT OF LIQUID NITROGEN LEVEL

• The evaporation rate of liquid nitrogen varies
  • From container to container
  • Temperature of the room in which stored
  • Number of times the container is opened.
• Hence periodic checking of level of liquid nitrogen is essential. The minimum level of liquid nitrogen should keep the straws completely submerged in the liquid nitrogen.
  • To measure the level of liquid nitrogen, a dipstick (slender stick made of wood or metal) should be used. The stick is gently lower into the container and rests it at the bottom.
  • Hollow tube should not be used. After 5-10 seconds take it out and wave in air.
  • The atmospheric air condenses as a frost on the dipstick to the level of liquid nitrogen.
  • Read the level one c.m below the end of frost line giving allowance for boiling of liquid nitrogen when dipstick is inserted.
  • By using calibration chart the volume of nitrogen can be estimated. Frequent measuring leads to unnecessary evaporation of liquid nitrogen.
• Weighment method
  • Specific gravity of liquid nitrogen is 0.82. (one litre of LN₂ = 0.82kg or one kg of LN₂ = 1.22 litres by volume).
  • Based on known weight of empty container and weight after filling liquid nitrogen, the assessment can be made.