PHOTOCHEMISTRY 299 



quantum yield is considerably reduced by collisions with foreign gases. 

 The effect of these foreign gases is rather specific, helium producing a 

 considerable effect. 



The photolysis of ozone is exceedingly complex, and in spite of a con- 

 siderable amount of work in various laboratories (24) the reaction is not 

 yet satisfactorily understood. In the presence of water vapor (18) the 

 quantum yield ranges from 1.6 to 130, indicating a chain mechanism. 

 The quantum yield varies inversely as a fixed power of the light intensity. 



Persulfate Ion. — When potassium persulfate is dissolved in water and 

 subjected to ultra-violet light between 2536 and 3020 A, oxygen is pro- 

 duced and the persulfate ion is changed to sulfate ion according to the 

 following reaction: 



S2O" + H2O + Av = 2SO7- + 2H+ + 1^02 



A quantum yield of unity was found for this reaction (11). In the 

 presence of potassium chloride or mercuric chloride it dropped to 0.7 of a 

 molecule per quantum. The work was carried out with a thermopile 

 and monochromator, using a quartz capillary lamp provided with a 

 magnetic field designed to extend the life of the lamp. 



REFERENCES. PART 2 



1. Allmand, a. J., and D. W. Style. The photolysis of aqueous hydrogen peroxide 

 sohitions. Jour. Chem. Soc. pp. 596-623. 1930. 



2. Backstrom, H. L. J. The chain-reaction theory of negative catalysis. Jour. 

 Amer. Chem. Soc. 49: 1460-1472. 1927. 



3. Bates, J. R., and H. S. Taylor. Studies in photosensitization. I. Jour. Amer. 

 Chem. Soc. 49 : 2438-2456. 1927. 



4. Bates, J. R., and H. S. Taylor. Studies in photosensitization. II. A source of 

 cadmium resonance radiation. Jour. Amer. Chem. Soc. 50: 771-773. 1928. 



5. Bauer, W. H., and F. Daniels. Separation of photochemical and thermal 

 action in the photobromination of cinnamic acid. Jour. Amer. Chem. Soc. 56: 

 378-385. 1934. 



6. Bauer, W. H., and F. Daniels. Oxygen a factor in the photobromination of 

 cinnamic acid. Jour. Amer. Chem. Soc. 56: 2014. 1934. 



7. Berthoud, a., and J. Beranek. Photochimie des halogenes. Addition du 

 brome a I'acide cinnamique et au stilbene. Jour. Chim. Phys. 24: 213-237. 

 1927. 



8. Bodenstein, M., and H. LtJTKEMEYER. Die photochemische Bildung von 

 Bromwasserstoff und die Bildungsgeschwindigkeit der Brommolektil aus den 

 Atomen. Zeitsch. Physik. Chem. 114: 208-236. 1925. 



9. Bodenstein, M., and F. Lieneweg. Unabhiingigkeit der Zersetzung des Jod- 

 wasserstoffs im Licht von Aggregatzustand imd Temperatur und Versuche zur 

 Deutung des Mechanismus des Vorgangs. Zeitsch. Physik. Chem. 119: 123-138. 

 1926. 



10. BoNHOEFFER, K. F. Auwendung der Quantentheorie auf photochemische 

 Sensibilisierungen. Zeitsch. Physik 13 : 94-105. 1923. 



11. Crist, R. H. The quantum efficiency of the photochemical decomposition of 

 potassium persulfate. Jour. Amer. Chem. Soc. 54 : 3939-3942. 1932. 



12. Damon, G. H., and F. Daniels. The photolysis of gaseous acetone and the 

 influence of water. Jour. Amer. Chem. Soc. 55: 2363-2375. 1933. 



