1907-8.] Combustion Analysis. 711 
If the substance contains nitrogen, a metallic copper spiral 7 cm. long is, 
as usual, placed at the front of the tube, and the current of oxygen is passed 
at a slower rate at the beginning of the combustion. For acetanilide the 
following percentages were obtained: — carbon, 71*03, 71*24; hydrogen, 6*72, 
6*89, the numbers for the formula C 8 H 9 NO being 71*11 and 6*67 
respectively. 
When the substance is a liquid it is weighed off in a small bulb with a 
sealed capillary, the tip of the capillary being broken off before its intro- 
duction into the tube. The best results are got when the capillary is 
comparatively wide and about 8 cm. long. The open end of the capillary, 
surrounded by the copper oxide, faces the stream of oxygen. The liquid, 
when the copper oxide in the front of the tube has reached dull redness, 
is slowly distilled out of the bulb into the copper oxide at the cool end 
of the tube by means of a small Bunsen flame applied directly to the upper 
side of the tube over the bulb. The combustion is then continued as for 
a solid. 
When a volatile liquid, such as benzene, is burned, it is introduced into 
the tube in a small sealed bulb terminating in a capillary at either end. 
The longer capillary (8 cm.) is plugged with fusible metal (compare Hempel, 
Gas Analysis, p. 341), and the shorter (3 cm.) is sealed off in the flame 
after the bulb has received its charge of benzene. In this case it is advisable 
not to surround the bulb and capillaries with copper oxide, but to leave the 
whole clear at the back of the tube. The little plug of fusible metal at the 
end facing the current of oxygen is melted by the application of the flame 
above the combustion tube, and the benzene is gradually vaporised by very 
gentle heating. The following result was obtained by this method : — 
carbon = 91*94 per cent., hydrogen = 7*83 per cent; calculated for C 6 H 6 — 
carbon = 92*31 per cent., hydrogen = 7*69 per cent. 
A combustion tube of the same dimensions may be used for estimating 
nitrogen by the direct method. In this case a current of carbon dioxide is 
substituted for the current of oxygen, the nitrogen being collected over 
concentrated potash solution. The reduced copper spiral necessary in this 
case need not exceed 7 cm. in length. The percentage of nitrogen in aniline 
found by this method was in two experiments 15*09 and 15*25, the 
percentage required for the formula C 6 H 7 N being 15*05. Equally 
satisfactory results were obtained with acetanilide and hippuric acid. 
To show that the method gives satisfactory results in the hands of 
a beginner, the following [consecutive analyses may be quoted from the 
notebook of a student who had no previous experience of organic 
combustions : — 
