84 SCIENCE PROGRESS 



effects of the silent discharge through gases at a low pressure 

 is mainly due to ultraviolet light, whilst at higher pressures 

 other agencies such as the cathodic rays come more promi- 

 nently into play. 



Thorough investigations of the action of ultraviolet light 

 on a mixture of carbon monoxide and steam and on a mixture 

 of hydrogen and oxygen would most probably furnish results 

 of considerable interest, especially as it has been shown 

 recently by W. Wieland x that formic acid is produced in 

 appreciable quantity by the interaction of carbon monoxide 

 and steam under certain conditions and F. Fischer and M. Wolf 2 

 have found that a very high percentage of hydrogen peroxide 

 may be produced by the action of the silent discharge on a 

 mixture of hydrogen and oxygen. 3 



Description of Actinometer 



Most of the experiments on the photochemical interaction 

 of chlorine and hydrogen described above can be performed 

 with the aid of the apparatus shown in the accompanying figure. 

 The hydrogen and chlorine are prepared by the electrolysis 01 

 concentrated chlorhydric acid contained in the large U-tube 

 on the left of the figure. The electrodes A and C, of graphite, 

 are fused into hard glass tubes which are ground into the 

 narrow ends a and 7 of the two limbs of the U-tube. The 

 circuit is closed by touching the tops of the two graphite sticks 

 with the copper wires which convey the current. The hydrogen 

 and chlorine generated by the electrolysis of the acid escape 

 through the capillary tubes fused into the necks of the two limbs 

 of the U-tube. By turning the three-way taps c and a into the 

 right positions either the hydrogen and chlorine can be per- 

 mitted to escape through the tubes x and y or conducted through 

 the taps b and d into the actinometer. The apparatus therefore 

 may be used to furnish a mixture of chlorine and hydrogen 

 in equivalent proportions or to prepare either of the gases 

 separately. The bottom of the U-tube is filled with glass beads 

 to prevent the movement of the saturated solution of chlorine 



1 Berichte, 1912, 45, 681. 2 Ibia. 191 1, 44, 2956. 



3 Both of these important discoveries are in complete harmony with Armstrong's 

 views on combustion. He has, in fact, predicted that the production of formic 

 acid would be found to be an intermediate stage in the combustion of moist 

 carbon monoxide. 



