Distilled Water - 6 fl. oz. - 180mL - 7 1/2 fl. oz.
Potassium Permanganate - 4 grains - 0.3g - 4 3/4 grains
Sodium Hydroxide (Caustic Soda) - 8 grains - 0.6g - 9 1/2 grains
Water (distilled) to make - 8 U.S. fl. oz. - 250mL - 10 Imp. fl. oz.

Formula given in U.S. Customary and metric measures. Imperial units accurate to within 1/4 gn. Liquid volumes converted in the ratio of 4 U.S. fl. oz. : 5 Imp. fl. oz.

FILMS OR PLATES: Take 8 ounces (250 cc. or 10 Imp. oz.) of pure water in a clear glass and add 1/4 dram (1 cc. or 1/3 dram) of Kodak HT-1a. Then take a 6-exposure film, size 3 1/4 x 4 1/4 in., or equivalent, from the wash water and allow the water from it to drip for 30 seconds into the glass of test solution. If a small percentage of hypo is present the violet color will turn orange in ABOUT 30 SECONDS and with a larger concentration the orange color will change to yellow. In either case the film should be returned to the wash water and washed until further test produces no change in the violet color.

PAPERS: Take 4 ounces (125 cc. or 5 Imp. oz.) of pure water in a clear glass and add 1/4 dram (1 cc. or 1/3 dram) of Kodak HT-1a. Pour 1/2 ounce (15 cc. or 5/8 ounce) of this solution into a clear 1-ounce glass container. Then take six (seven if using the Imperial formula) prints, size 4 x 5 in., or equivalent, from the wash water and allow the water from them to drip for 30 seconds into the 1/2 ounce of the dilute test solution. If a small quantity of hypo is present the violet color will turn orange in ABOUT 30 SECONDS and become colorless in one minute. In either case the prints should be returned to the wash water and washed until further testing shows no change in color.

Traces of hypo retained in films or prints greatly acceleartes the rate of fading of the image. It is extremely difficult to test for small quantities of hypo, but this test will indicate when the film or prints may be considered reasonably free from hypo. Even if the print test results in a negative reaction, it is still no guarantee that they may not ultimately fade.

NOTE--Oxidizable organic matter if present in the water reacts with the permanganate solution and changes its color in the same manner as hypo. The water should therefore be tested as follows:

Prepare two samples of the permanganate test solution explained above. Then add a volume of tap water to one test sample equal to that of the wash water with the film or prints into the other sample. If the sample to which tap water has been added remains a violet color, this indicates the absence of organic matter and it will be unnecessary to make the test in duplicate. If the color is changed slightly by the tap water, however, the presence of hypo in the film or prints will be shown by the relative color change of the two samples. For example, if the tap water sample turned pink and the wash water sample became yellow it would indicate the presence of hypo, while if both remained the same shade, this would indicate the absence of hypo.

When complete removal of hypo is important, prints should be treated in the Kodak HE-1 Hypo Eliminator or another wash aid.