BY J. BROWNLIE HENDERSON, AND P. W. JONES. 55 
first two hours and 0.2 milligrams in the second two hours, 
.the sublimed mercury from the silver being again easily 
recognised under the microscope. In this experiment 
a third silver leaf was inserted in the tube close to the others 
and tested separately for mercury in the sublimation tube, 
but none was obtained, again confirming the result that air 
passing at the rate of 8 litres per hour carried no mercuric 
chloride past the first two leaves. Judging by appearance; 
the whole of the mercuric chloride is absorbed by the first 
5 mm. of silver leaf. 
From the above results it seems that not only does 
the method afford a rapid and easy means of detecting 
the presence of mercuric chloride in explosives, but enables 
a fair estimation to be made of the quantity present. 
