68 THE ROYAL SOCIETY OF CANADA 
Washing with different amounts of washing solution has no ap- 
preciable effect on the occlusion. It was further shown that occlusion 
takes place at the time of precipitation and it is not brought about by 
allowing a precipitate to stand in contact with an iron solution. 
The occlusion is apparently due to the formation of a definite 
chemical compound. 
University of British Columbia, 
Syracuse University. 
