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1949 PHOTOGRAPHIC DEVELOPERS 279
analysis of the used developer, then this curve should be identical with the curve of Elon and hydroquinone at these concentrations (i.e., 5.51 grams per liter of Elon and 2.48 grams per liter of hydroquinone).
Accordingly, a fresh developer was prepared with Elon concentration at 5.51 grams per liter and hydroquinone concentration at 2.48 grams per liter. The absorption curve of this mix is shown in Fig. 7. The close similarity of these two curves shows that the material extracted by the ethyl acetate was Elon and hydroquinone.
The results of this experiment show that the presence of the oxidation products of Elon and hydroquinone had no measurable effect upon the analysis. Other developer solutions which have contained larger and smaller amounts of oxidized Elon and hydroquinone have been analyzed, and it seems likely that large variations in the amount of oxidized material do not markedly affect the determination.
EFFECT OF BUFFER pR UPON THE ANALYTICAL RESULTS
The pH. of the acetate buffer was varied by changing the ratio of sodium acetate and acetic acid, and the absorbancy indices of Elon and hydroquinone determined. The results are shown in Table II and
TABLE II CHANGE IN ABSORBANCY INDICES WITH CHANGE IN pH OF BUFFER
• Elon .
' — Hydroquinone —
PH
290 m/i
270 rn/z
290 HIM
270 mju
4.96
0.009
0.071
0.022
0.081
5.05
0.010
0.071
0.022
0.080
5.17
0.013
0.070
0.022
0.081
5.42
0.019
0.068
0.022
0.082
TABLE III EFFECT OF pH OF BUFFER
pH of Buffer
Hydroquinone, Grams per Liter
Elon, Grams per Liter
4.90 4.99 5.08
2.89 2.93 2.98
6.12 5.97 5.95