217 



liieces of zinc cniitainod in ;i Sii^i douliU' pipet for solids. Tlie pipt't was 

 lillcd with hoilod distillod water to displace the air. The sulphuric acid 

 was added tlimuuh a ulass tnlie which entered throui^li the opening for the 

 introdnction of solids into tlie pipet. The hydrogen gas was allowed to 

 escape completely from tlie api)aratus several times before any was saved 

 Icr analysis. This form of generator very eifectively protected the hydro- 

 gen gas from the diffusion of air. The results are given in tlie following 

 table : 



Tlie following table shows the results which were obtained in the 

 analysis of gas residues : 



Eesidue Oxygen Volume after j- To al Caib.n 



ec. CO. Combustion. "*^ Contraction. Dioxide. 



51.9 80.4 50.2 82.1 18.8 



52.3 7J.3 42.4 3 81.4 17.5 



52.16 67.18 38. 2 81.34 17.77 



The result in experiment 1 was obtained witli the ordinary combustion 

 pipet. This value was talcen as the standard. Experiment 2 in the table 

 shows 17.5 per cent, of carbon dioxide, which was of course obtained by the 

 absorption of tlie carbon dioxide which was in the buret. This value must 

 be corrected for tlie amount of carbon dioxide which remained in the 

 quartz tube. The total gas residue after conibustion (including the air 

 originally in the quartz tul)e) was 42.4 plus 2.795 (the volume of the quartz 

 tube which \vas unoccupied by platinum) which was 45.195. So 93.8. 

 (42.4-^45.195), was the per cent, of the gas which was measured in the 

 buret. 



All of the results given in the tables show that the (piartz tube is as 

 accurate as the combustion pipet. It was found necessary to pass tiir 

 through the quartz tube to remove the carlwn dioxide produced by one 

 experiment if another experiment was to be made at once. If only total 

 contraction was desired the carbon dioxide did not need to be removed. If 

 nitrogen was to be determined the gas remaining in the tube from a jirevi- 

 ous experiment had to be removed by passing air. 



This apparatus gave an excellent method of determining the total 

 nitrogen in gas. The gas was mixed with an excess of oxygen whose nitro- 



15—33213 



