DISPOSAL OF EXCEETA 381 



Sometimes the test is made more severe by pumping in 

 smoke from a generating apparatus. There are special 

 drain grenades made consisting of a mixture of phos- 

 phorus and assafcetida ; the grenade is inserted and 

 the drain closed; a little water poured down ignites the 

 phosphorus, and dense fumes with the penetrating odour 

 of assafcetida are given off, the latter if escaping being 

 readily recognised by its smell. 



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