The importance of convection in the determination of the water vapour conductance of avian egg shells

Abstract

1. It was confirmed that convection across the avian egg shell surface does not affect diffusive transport of water vapour through the shell.

2. Relative water vapour conductance, i.e. the ratio between the water vapour conductance as determined in a desiccator and the actual water vapour conductance, as well as relative humidity in the desiccator are influenced by the total rate of water loss of the eggs in the desiccator.

3. The total rate of water loss is influenced by the number of eggs in the batch, their average actual water vapour conductance, desiccator temperature and barometric pressure.

4. Therefore water vapour conductance is easily underestimated, in particular when determined in still air at a small surface area of desiccant.

5. All the above effects are considerably reduced by convection.

6. Further improvements in technique are suggested, particularly for practice where determinations have to be made for a relatively large batch of eggs.