299 



If the hypothesis advanced in the foregoing is correct, 

 and it can be definitely proved that an insoluble silver sodium 

 thiosulphate does remain behind in the film of photographs, 

 then it is to be considered as to whether or not this should 

 not always be removed in all photographic prints, whether for 

 toning or not. According to present knowledge upon the 

 subject, its presence can do no good, and presumably, in course 

 of time, may be responsible for the deterioration of the 

 image. 



References. 



1. 1918. Roebuck: ''The Science and Practice of Photo- 



graphy," p. 132. 



2. 1906. Smith: "Intro, to General Inorg. Chemistry," 



p. 173. 



3. 1920. Greenall : ''British Journ. Photo. Almanac for 



1920," p. 481. 



4. 1906. Derr: "Photography for Students of Phys. and 



Chem.," p. 146. 



5. 1918. Roebuck: Loc. cit., pp. 9, 18. 



6. 1911. "Cassell's Cyclopaedia of Photography," p. 253. 



7. 1896. Comey: "A Diet, of Chemical Solubilities 



Inorg.," p. 475. 



8. 1898. MuiR and Morley : "Watts' Diet, of Chem.," 



vol. iv., p. 707. 



9. 1918. Roebuck: Loc. cit., p. 108. 



10. 1894. MuiR and Morley: "Watts' Diet, of Chem.,'' 



vol. ii., pp. 334, 337. 



11. 1911. "Cassell's Cyclopaedia of Photography," p. 298. 



12. 1896. Comey: Loc. cit., p. 469. 



13. 1911. RoscoE and Schorlemmer : "A Treatise on 



Chem.," vol. i., p. 461. 



