1911-12.] Note on a Perforated Silica Plate. 
17 
IV. — Note on a Perforated Silica Plate for excluding Flame 
Gases from a Crucible during Ignition. By Alexander 
Charles Cumming. 
(MS. received November 9, 1911. Read December 4, 1911.) 
The device shown in the accompanying sketch has been in use in the 
Chemistry Department of the University of Edinburgh for some time. It 
consists of a silica plate, 5 inches square, with a hole bored in it of such 
size as to admit a crucible to one-half of its depth. The silica plate is held 
in an inclined position by a clamp. 
By this means the flame gases are excluded from the interior of the 
crucible during an ignition. With this device calcium carbonate in a 
platinum crucible is quickly reduced to oxide with a good bunsen burner, 
while with a Meeker burner the reduction is complete in a few minutes 
even when a porcelain crucible is used. The device is also useful for cases 
such as the ignition of nickel oxide, where there is a danger of reduction. 
For the estimation of sulphur in coal some such device is absolutely 
necessary to exclude the flame gases. 
The original idea is due to J. Lowe, who used clay discs. Hillebrand 
VOL. xxxii. 2 
