218 



gen contents was accurately determined. After combustion in tiie quartz 

 tube, the gas was passed into potassium hydroxide and allvaline pyrogallol 

 pipets. The unabsorbed residue consisted of the nitrogen in the gas and 

 the nitrogen which was in the oxygen. The results are as follows : 



Other tests showed that under the conditions of the experiment less 

 than 67.7 cc. of the oxygen (63.4 cc. of pure oxygen) did not give com- 

 plete combustion with 50 cc. of the gas. This was 12 cc. of pure oxygen 

 in excess. 



SUMMARY. 



Gas residues after the addition of oxygen gas were burned by passing 

 them through a heated quartz tube which contained pieces of scrap plati- 

 num. The results are very accurate. 



The advantages of tjiis apptiratus over the standard combustion 

 pipet are; 



1. The quartz tube and pieces of platinum are not easily broken or 

 damaged during use. The quartz tube, however, is brittle and will break 

 if struck a blow. The combustion pipet is very easily broken and the small 

 platinum wire often burns out even when great care is exercised by the 

 operator. 



2. No metal or other substance wliich can be oxidized or acted upon 

 by any of the gases is present in tlie quartz tube during the burning. In 

 tlie combustion pipet, mercury, an oxidizable metal, is always i)rest'nt. In 

 some of the experiments during this research, the conditions were such that 

 very serious errors were made by the absorption of gasi's by the mercury. 

 Everyone is familiar with the formation of o.xidcs upon the mercury and 

 upon the sides of the combustion pipet, 



.■'>. Small cracks in the glass tubes, or leaks around tlic nibbcr stopjuT 

 or jibu'cs where glass tubes enter, in the conilnistion piiirts cause serious 

 errors. There is very little chance for leaks in the quartz tube appamtus. 



4. Platinum scrap such as short lengths of wire which is generally 

 plentiful in laboratories, is used in this apjiaratus. The quai'tz tubes 

 are cheap. 



The disadvantages of tins new jirocess are; , 



