The procedure for conducting a test for causticity with tannin is as follows: 1.   Fill two test tubes to the first mark (25 ml) with some of the original boiler water sample, taking care not to disturb the settled sludge in the container. (Transfer as little sludge as possible from the sample-collecting container to the test tubes.) 2. Shake causticity reagent No. 1 thoroughly and add enough to each of the two marked tubes to bring the levels up to the second, or long, mark (30 ml). Stir both with  the  stirring  rod,  which  must  be  kept  clean  and reserved for the causticity test only. 3. Stopper both tubes and let them stand until any sludge  formed  has  settled  to  the  bottom.  The  sludge carries down with it much of the tannin or other colored matter in the solution; settling takes a few minutes if the sample is warm. 4.  Without  disturbing  the  sludge  at  the  bottom, pour  enough  solution  from  the  tubes  into  the  third marked  tube  to  fill  it  to  the  second,  or  long,  mark. Discard  the  mixture  left  in  the  first  two.  When  the sample in the third tube is still warm, cool it by letting cold water run on the outside of the tube. It is sometimes possible to intensify the pink color by adding two drops of phenolphthalein from the indicator-dropping bottle to the sample in the tube. Stir the solution. When it is not pink, the causticity in the boiler water is zero. 5.   When the sample is not pink, the test is finished. But  if  the  mixture  turns  pink,  proceed  in  the  same manner as directed in Steps 3, 4, and 5 when no tannin is used. Here  is  a  brief  explanation  of  an  ALTERNATE PROCEDURE for making the test for causticity when tannin is used. In this procedure any glass container, such as a large test tube or graduated cylinder, marked for 50 to 60 ml can be used instead of the two standard marked test tubes used in Steps 1 and 2 above. With the large test tube or graduated cylinder, the warm (160°F) sample is added up to the 50-ml mark and causticity reagent No. 1 up to the 60-ml mark. Stir the mixture and  stopper  the  tube,  or  graduate.  After  the  sludge settles, pour off enough of the solution into one of the standard marked test tubes to fill it to the long mark (30 ml). When the sample is warm, cool it by letting cold water run on the outside of the tube. Adding two drops of  phenolphthalein  may  intensify  the  pink  color. When  the  solution  is  not  pink,  the  causticity  in  the boiler water is zero. But if it turns pink, proceed in the same manner as in Steps 3, 4, and 5 when no tannin is used. 1-32 Test for Sodium Sulfite The sample for this test should be cooled to 70°F, or below, and exposed to the air as little as possible, because   oxygen   in   the   air   combines   with   sodium sulfite in the sample and causes low readings. Collect a separate sample, using the boiler water sample cooler, with  the  line  reading  to  the  bottom  of  the  sampling bottle.  Allow  the  boiler  water  to  run  until  a  few bottlefuls overflow to waste. The  equipment  necessary  to  make  the  sodium sulfite test is as follows: One  30-ml  acid-dropping  bottle,  with  dropper marked at 0.5 ml for hydrochloric acid 3N One 30-ml starch-dropping bottle, with dropper marked at 0.5 ml for starch indicator One 150-ml beaker One stopper for plain test tube One stirring rod One 8-in. dropper One 1/4-measuring tsp One 50-ml beaker Two plain test tubes Two marked test tubes The reagents required are as follows: One 2-oz bottle of potato, or arrowroot starch One 8-ml vial of thymol One 24-oz bottle of hydrochloric acid 3N One  1-pt  amber  bottle  of  standard  potassium iodate-iodide   reagent The starch indicator for this test must be prepared locally. The procedure to adhere for good results is as follows: 1. Measure out a level one-fourth tsp of potato or arrowroot starch and transfer it to the 50-ml beaker. 2. Add a few milliliters of distilled water and stir the starch into a thick paste, using the end of the stirring rod. 3.  Put  50  ml  of  distilled  water  into  the  150-ml beaker. (It is convenient in this step to have the 150-ml beaker marked at the point where it holds 50 ml, or one of the marked test tubes can be used by filling it with distilled water to the fourth mark above the long mark.)