358 Determination of Carbon in Graphite. 
was then washed and dried. [t still retained much adhering sili- 
these numbers, 16°61, corresponds in 100 grs., to carbon, 75°5 grs. 
Black Carbonaceous Sublimate-—This material was collected 
from the interior of a flue used for burning the native carburetted 
hydrogen, so extensively employed some years ago as a fuel, at 
many of the salt-works in the Kenawha Valley, Virginia. It is 
very light, of a spongy texture, harsh to the touch, hard enough 
ost compact to scratch glass, and of a deep black color 
externally, passing into greyish black within. 
Finding by some preliminary experiments, that it resisted ox- 
ydation even more powerfully than graphite, we subjected it to 
still longer trituration with the silica than we had a necessa- 
ry with the graphite, and we employed in the oxydation a some- 
what greater excess of sulphuric acid than in the preceding cases. 
‘The evolution of CO, did not begin until the lamp had been ap- 
plied for several minutes, and its progress was much slower than 
with the graphite, the complete oxydation requiring nearly an hour. 
ix grains of this material, previously well calcined to remove 
moisture or other volatile matters, yielded carbonic acid, 21°62 
grs.; corresponding in 100 grs. of the calcined sublimate, to car- 
bon, 98-2 grs. 
As a means of testing in some measure the accuracy of the 
process above described, the following experiments were made to 
determine the carbon of the graphite (a) and the black sub- 
limate, by burning a weighed quantity of these substances in 
oxygen. 
The apparatus employed for burning the graphite was a spa- 
cious platinum crucible, through the cover of which was passed @ 
pipe connected with an oxygen gasometer so as to supply a gentle 
stream of this gas to the ignited materials. By previous trials, it 
was found that the black sublimate could be readily burned in & 
current of oxygen passed over it in a tube of refractory glass, and 
this method was accordingly used for its oxydation. 
Before triturating the graphite with the silica, the latter was in- 
tensely ignited to drive off the trace of moisture which it hac 
been found to contain. ‘Twelve grains of graphite (a) thoroughly 
ground with the silica thus prepared, were exposed in the pla- 
tinum crucible to a bright red heat, the interior being supplied 
continually with exygen from the gasometer. In about fifty 
minutes the carbon of the graphite was entirely consumed. ‘The 
residue had a faint brownish tint, while the unmixed silica sim!- 
larly ignited, was found to retain its original whiteness almost uu- 
altered. This slight colorarion of the former was doubtless 
to the trace of iron present in the graphite. — on 
i ge ee a 
