DEVELOPERS AND THEORY OF DEVELOPMENT 345 



"Blue-black" Agents 

 Quinine hydrochloride 

 Quinoline 

 Formocystine 

 5-Nitrobenziminazole 

 2, 4, 6-Trimethylphridine 

 Triazole 

 Benzotriazole 

 Iminazole 



2-Methylbenzoxazole 

 2-Methylnaphthothiazole 

 Pseudo-thiohj'dantoin 

 Diphenyhodonium nitrate 

 lodophenyl-phenyHodonium chloride 



These blue-black agents are used in developers at concentrations around 1 part in 

 1000 to 1 part in 10,000. Like the antifogging agents, even a slight addition of these 

 agents retards the initial appearance of the image and generally prolongs the time for 

 complete development. 



Additions for Fine-grain Development. — In the effort to secure fine grain many 

 other compounds have been added to developers. Work of this kind is particularly 

 difficult, as there is no universally accepted way of measuring graininess, and hours of 

 painstaking work must go into the evaluation of any change. It is not surprising 

 therefore to find disagreements between workers and even contradictory results in 

 repeated tests under supposedly similar conditions. 



Opposed to the careful and painstaking work done by some, there are many evi- 

 dences of mysticism and wishful thinking in this phase of the literature of photog- 

 raphy. To illustrate the wide range of additions which have been tried, the following 

 list was prepared, covering additions suggested for p-phenylenediamine developers. 

 This list is presented without any attempt at judgment of the value of the suggestion 

 but only to show the range of materials. 



Additions Suggested for Paraphenylenediamine Developers 



Other reducing agents: 



Metol 



Hydroquinone 



Pyrogallol 



jo-Aminophenol 



Pyrocatechol 



Rubinol (alkyl-substituted pj^rogallol) 



Resorcinol 



Glycine 



Alkali agents recommended: 



Sodium carbonate 

 Lithium hydroxide 

 Disodium hj^drogen phosphate 

 Trisodium phosphate 

 Ammonium hj'droxidc 

 Ammonium carbonate 

 Potassium carbonate 



