544 Dr. Kolbe on the Formation of Nitric Acid in 



over mercury, and after having exploded the mixture, I ob- 

 served the diminution of the volume of gas. 



[The volumes found by observation in this and the follow- 

 ing examples were saturated with the vapour of water.] 



Experiment II. 



Hydrogen. . . . 115-5 12-0°C. 764*7 mm 297*9 mm 63*6 

 After admission of O. 281-4 11*5 ... 162-1 159*9 



After combustion . 146*5 11-3 ... 296-5 64*4 



When we calculate the quantity of the consumed hydrogen 

 from the whole volume of gas which has disappeared by com- 

 bustion, we find numbers which correspond exactly with the 

 hydrogen used. 



* I. II. 



Hydrogen used .... 29*4 63*6 



calculated . . 29-4 63-6 



By this similarity of the results as found and calculated, it is 

 evident that the mercury cannot become oxidized when pure 

 hydrogen is burnt with an excess of oxygen. Mercury sub- 

 limed also in this case ; but no trace of the crystals spoken 

 of could be seen, even when the residual gas was dried. 



Varying the experiments, I mixed with a similar explosive 

 mixture a small portion of atmospheric air (which is calcu- 

 lated to contain in 100 vols. 20 - 9 vols, of oxygen) ; I obtained 

 the following results, very different from the former : — 



Experiment III. Height of 



mercury in 

 tube over 

 that in 

 Vol. obs. Temp. Barom. trough. Corr.vol. 

 Atmospheric air . . 76-8 8'8 G C. 767'9 mm 367'2 mm 29-2 

 AfteradmissionofH. 246-0 8-8 768*2 197*0 134*1 

 AfteradmissionofO. 402*9 9*5 768*3 45*8 277*8 



After combustion .225*1 9*6 768*4 218*2 117*8 



with a correctly graduated millimetre-scale etched upon the glass, and ex- 

 actly graduated, on which by employing a mirror it was easy to determine 

 the tenth part of a millimetre. 1 also took care to observe all the precau- 

 tions, by which Bunsen has excluded everything that can occasion an error. 

 The mercury was previously purified by digesting for some days with nitric 

 acid, and had all the properties of the pure metal. 



