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1949
PHOTOGRAPHIC DEVELOPERS
271
water. Adjust the final pR of the solution to 5.00 =*= 0.02 with glacial acetic acid or sodium hydroxide.
Cleaning solution. Mix one volume of denatured alcohol and one volume of 3 normal hydrochloric acid.
Apparatus
Beckman Spectrophotometer, Model DU, with ultraviolet accessories.
Fused silica absorption cells, 1 centimeter.
Procedure
Dilute 1.00 milliliter of sample with 100 milliliters of pH. 5 acetate buffer. Determine the absorbancy of this solution at 270 and 290 millimicrons.
NOTE: Distilled water was
used in the blank cell as a reference liquid. Care must be
taken to see that the distilled
water and the acetate buffer
do not stand in contact with
rubber or plastic tubing as
material is leached from these
substances that can cause
serious errors in the analysis.
In this laboratory, the reagents are allowed to flow in
glass tubing with only very
short connections of plastic or
rubber tubing. The silica
cells are cleaned before each
analysis with acid-alcohol
cleaning solution and rinsed with distilled water.
Determine the absorbancy of a "basic mix" at 270 and 290 milliticrons after diluting 1 milliliter with 100 milliliters of pH. 5 acetate iflfer. Subtract the absorbancies of the basic mix from the absorbicies of the sample. Determine the concentrations from a
240 26O 280 300 320 34O
Wov«length mM
Fig. 1 — Typical absorption curves.
A, Elon, concentration 5 grams per liter.
B, hydroquinone, concentration 5 grams per liter.
C, Elon and hydroquinone, concentration 5 grams per liter.