We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
Fine-Grain Developers — Carlton and Crahtree 425
Bubbling air through the developer increased the rate of development. This fact is not readily explained, but indicates that the quantity of carbon dioxide present in the air has no perceptible effect on the rate of 'development.
Table V Ejfect of Aeration on the Rate of Development
1£ min.
15 min.
18 min.
21 min.
gamma
gamma
gamma
gamma
Eegular borax
■ 0.72
0.80
0.92
0.97
Aerated for 5 hours
.81
.93
1.04
1.09
Bubbled with carbon
dioxide
for 4 hours
.15
..36
.47
.52
B. With Use
1. The Chemistry OF Development, (a) During development a very complex chemical reaction takes place between the silver halide in the emulsion and the developer. In the case of a negative emulsion the silver halide may be considered to consist essentially of silver bromide which reacts with a hydroquinone developer as follows:
Silver bromide + alkali + sodium sulfite + hydroquinone = Silver + sodium bromide + hydroquinone sulfonates.
Quinone is probably an important intermediate product but it reacts at once with the sulfite to give hydroquinone monosulfonate.^"^ This is a developing agent and may go through the cycle again to give hydroquinone disulfonate as a final product. Elon probably gives similar reaction products because the amino-phenols, of which Elon is a member, are very easily oxidized to quinone.
The by-products of development, sodium bromide, sodium iodide, and the disulfonates of hydroquinone which accumulate in the used developer have a retarding action on development. As development progresses, the supply of developing agents is therefore slowly used up and the products of development accumulate so that a point is finally reached where there is a serious drop in the rate of development and the speed of the emulsion. The quantity of film that can be processed before this occurs determines the life of the developer.
A partially exhausted developer, however, can be rejuvenated by the addition of a fresh supply of developing agents so that it can go through another period of usefulness before it becomes exhausted.