The equipment required is as follows:

Two 8-in. droppers with bulbs

Two 250-ml glass-stoppered bottles or flasks labeled causticity No. 1 and causticity No. 2

Four marked test tubes, 22 mm by 185 mm

Three plain test tubes, 22 mm by 175 mm

Three rubber stoppers, No. 2

One 14-in. test-tube brush

One test-tube clamp

Two 9-in. stirring rods

One 1-oz indicator dropping bottle for phenolphthalein

One test-tube rack

The following reagents also are required:

One 24-oz bottle or flask causticity reagent No. 1

One 24-oz bottle or flask causticity reagent No. 2

One 4-oz bottle phenolphthalein indicator

The following are the steps to follow in conducting a test for causticity when tannin is not used:

CAUTION

Avoid exposure of the sample to the air as much as possible to reduce absorption of the CO₂ .

1. Without disturbing the settled sludge, fill a marked test tube exactly to the first mark (25 ml) with some of the original boiler water sample.

2. Shake causticity reagent No. 1 (barium chloride solution saturated with phenolphthalein) thoroughly and add enough to the graduated tube to bring the level exactly to the second, or long, mark (30 ml).

3. Stir the solution with the 9-inch stirring rod, which must be kept clean and reserved for the causticity test only. When the mixture remains colorless or does not turn pink, the causticity in the boiler water is zero and the test is finished. When the mixture turns pink, causticity is present. (If the pink color is not deep, intensify it by adding two drops of phenolphthalein indicator to the mixture in the tube.) Add causticity reagent No. 2 (standard one-thirtieth normal acid), using the 8-inch dropper, thatch must be kept clean and reserved for the causticity test only. Causticity reagent No. 2 is sucked from the reagent bottle into the dropper by its rubber bulb and added, drop by drop, to the test tube. After each addition, stir the mixture with a stirring rod. After sufficient reagent has been added, the pink color disappears; the change point is usually sharp. As soon as the pink color just fades out, stop adding the reagent.

4. The amount of causticity reagent No. 2 required to make the pink color disappear shows the concentration of hydroxide (OH) or causticity in the boiler water. The amount of reagent used is shown by the marks on the test tube above the long mark (30 ml). The distance between any two marks on the test tube equals 5 ml, and readings less than 5 ml can be estimated. For example, when only three fifths of the distance between the long mark and the next mark above were filled, then 3 ml was added. When the distance filled was past one mark plus three fifths of the distance to the next, then 5 + 3 = 8 ml was used. To obtain the actual ppm of hydroxide or causticity shown by the test, multiply the number of ml by 23. This constant number, 23, represents the amount of sodium hydroxide in the boiler water by volume. Thus, for 8 ml of causticity reagent No. 2, there are 8 x 23 = 184 ppm hydroxide or causticity in the water.

5. Record the results of the test in a boiler log or chemical log and adjust the range to meet requirements. When causticity is too high, blow down; if too low, add sodium hydroxide (caustic soda).

Test for Caustic Alkalinity (OH) with Tannin

For this test, start with a warm sample of about 160F. It may be reheated by placing the sample-collecting container in a stream of hot boiler water drawn through the boiler water cooler connection. In a test for causticity when tannin is used, make sure you observe the same precautions as carefully as when tannin is not used.

CAUTION

Avoid exposure of the sample to the air as much as possible to reduce absorption of the CO₂ .

The equipment and reagents required for this test are the same as those listed in the preceding section where tannin was not used.