428 PROFESSOR J. W. MALLET ON THE ATOMIC WEIGHT OF GOLD. 
temperature, immersing the body of the globe in an outer vessel of mercury so as to 
prevent extension or flexure of the glass by the weight of the contained metal, filling 
up to the very mouth with mercury, inserting the stopper with the stopcock open, 
thus forcing out through its orifice the last of the air, closing the stopcock, removing 
from the orifice tube, by an iron wire, the drop or two of mercury remaining in it, and 
then emptying the flask, and carefully weighing in successive portions the mercury 
which it had held. The hydrogen from the voltameter was collected in this flask, 
without its stopper, the flask liaving been previously filled with mercury, with the 
needful precautions for removal of all air, and inverted over a mercury trough. In 
each experiment the process of electrolysis was arrested wlien the hydrogen had filled 
Fig. 7. 
the body of the globe and reached to a point rather more than half way down the 
lengtli of the neck, the gold plates being of course withdrawn at the same moment 
from their cell of gold solution, set away to soak in distilled water, and afterwards 
thoroughly washed, dried, heated in the Sprengel vacuum, cooled, and weighed. The 
portion of hydrogen collected was dried by successive halls of fused potash introduced 
and withdrawn by means of platinum wire. The neck of the flask having, in advance 
of the collection of hydrogen, been passed through a cork, this was used to close the 
mouth, placed downwards, of a vessel through which a stream of water was caused to 
flow rapidly from the pipes supplying the University buildings. The atmospheric 
temperature of the day on which the electrolysis experiment was made having been 
such as not to differ too much from the temperature of the water from the pipes, the 
gas occupied such a volume after effectual exposure to this latter temperature that 
