METHOD OF MANIPULATION 419 



is shown in the figure. When the stopper is well ground and 

 greased the reduction tube may be raised or lowered as much as 

 may be necessary without any danger of escape or entrance of 

 gas. To determine the position of the reduction tube C the 

 reading of the barometer and thermometer at room temperature 

 is taken. From the reading of the barometer subtract one milli- 

 meter if the temperature be below 12, two millimeters at a 

 temperature from 12 to 19, three from 20 to 25, and four 

 above 25. 



When a gas has been introduced into the measuring tube A 

 ir is brought to the volume which it would assume under stand- 

 ard conditions by adjusting the tube C, in such a way as to bring 

 the mercury in C and A to the same height and the surface 

 of the mercury in C is exactly at 100 cubic centimeters. The 

 gas in A is then at the volume which it would occupy under 

 standard conditions, and this volume can be directly read. This 

 adjustment is secured by moving the tubes B and C up or down. 

 If gases are to be measured wet, a drop of water should be put 

 on the side of the upper part of C, and if dry, of sulfuric acid, 

 before the adjustment for temperature and pressure. 



363. Method of Manipulation. By the action of mercury in 

 the presence of sulfuric acid, the nitrogen in nitrates, nitrites, 

 nitrosulfates, nitroses, nitrocellulose, nitroglycerol, and the greater 

 number of explosives, may be obtained and measured as nitric 

 oxid. The nitrogen compounds are decomposed in the apparatus 

 shown in Fig. 30. 



To make an analysis, the apparatus is filled with mercury, 

 through F, until the two openings in the cock and i are entirely 

 occupied with that liquid. The cock h is then closed, and the 

 nitrogen compound, in solution, introduced through g, care being 

 taken that no air enters g when F is depressed and h opened to 

 admit the sample. The funnel g is washed several times with a 

 few drops of sulfuric acid, which are successively introduced into 

 G. The total liquid introduced should not exceed 10 or 15 cubic 

 centimeters, of which the greater part should be sulfuric acid. 

 The rubber tube connecting G and F is carefully closed with a 

 clamp and G violently shaken for a few minutes until no further 



