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.
418
Transactions of S.M.P.E., Vol. XIII, No. 38, 1929
2. Effect of Varying the Alkalinity. The alkalinity of a
developer may be expressed in terms of the pH value which is the
logarithm of the reciprocal of the hydrogen ion concentration, viz. :
1 pH = log —
Lh where CH is the concentration of hydrogen ions in the solution. ^^ The absolute accuracy of the pH values is open to question, but the measured relative values have been correlated verv satisfactorilv
Figure 3. Time-Gamma Curves for the Eegular Borax Developer (A) and with Half Concentration of Borax and Developing Agents (B). (Rack and Tank Method at 65°F.)
(Eastman Negative Panchromatic Motion Picture Film, Type 2).
by a study of the rate of development of experimental developers. Solutions with pH values about 7.0 are alkaline and the alkalinity increases with the pH value. Slightly alkaline developers like the present borax developer lie in the pH range from 8.0 to 9.0 and the more alkaline developers like sodium carbonate and caustic alkaline developers lie in the range from 11 to 14.
The pH values were determined by the LaMotte hydrogen ion apparatus which works upon the principle of color change of organic indicator dyes and when used for this purpose may be in error by ±0.1 pH. Developers from Nos. 1 to 6 indicate that the potassium bromide content has no effect on the alkalinity but the alkalinity increases with the borax content and decreases with increased Elon content. The addition of hydroquinone decreases the alkalinity but