218 



gen contents was accurately determined. After combustion in the quartz 

 tube, the gas was passed into potassium hydroxide and alkaline 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 i»ure oxygen 

 in excess. 



SUMM.\KY. 



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

 fhem through a heatetl quartz tube which containetl i)ieces of scrap plati- 

 num. The results are very accurate. 



The advantages of tJUis ajjparatus uvcr the standard combustion 

 pil)et are: 



1. The quartz tube and i)ieces of platinum are not easily broken or 

 daniage<l during use. The quartz tube, liowever, is brittle and will bi'eak 

 if struck a blow. 'I'lic combustion jiipet is very easily broken and the small 

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

 • ►lierator. 



2. No metal or other substance wiiicli can be oxidizetl or acted uiioii 

 by any of the gases is jiresent in the (juartz tube during the burning:. In 

 the combustion pipet, mercury, an oxidizable metal, is always present. In 

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

 vei-y serious errors were ma(h' by the absorption of gases by the mcr( my. 

 Everyone is familiar with the formation of oxides upon the mercury ;ind 

 upon the sides of the combustion pipet 



3. Small cracks in the glass tul)es. oi' leaks around the rubber stopper 

 or i)laces where gla.ss tubes enter, in the combustion pipets cause serious 

 errors. There is verj- little chance for leaks in the quartz tube apparatus. 



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

 plentiful in laboratories, is used in this aitjiaratus. The quartz tubes 

 are cheap. 



The disadvantages of this new process are: 



