4.   Bring the water in the 150-ml beaker to a boil by any convenient method. 5.  Remove  the  source  of  heat  and  immediately pour the starch paste into the boiling water while stirring the  solution. 6. Put a crystal of thymol into the starch solution and  stir.  After  the  solution  has  cooled,  pour  off  any scum  on  the  surface  and  transfer  30  ml  to  the indicator-dropping   bottle. 7.  The  starch  solution  loses  its  sensitivity  as  an indicator  after  a  time.  Addition  of  the  thymol  preserves it for about 2 weeks. The starch should be dated when prepared. In  making  the  sodium  sulfite  test,  proceed  as follows: 1.   Transfer 1 ml of hydrochloric acid 3N to a clean, marked test tube by measuring out 0.5-ml portions with the dropper of the acid-dropping bottle. 2.   From  the  starch-dropping  bottle,  transfer  0.5  ml of starch to the marked test tube. 3.  Without  disturbing  any  settled  sludge  in  the sample, pour enough of the sample into the marked test tube to bring the level up to the first mark (25-ml). Stir the  mixture  in  the  tube  with  the  plunger  end  of  the stirring  rod. 4.  To  add  the  standard  potassium  iodate-iodide reagent to the mixture in the marked test tube, have the marked test tube supported and the stirring rod placed in the  tube,  so  the  reagent  can  be  added  with  one  hand while  the  mixture  is  stirred  with  the  other.  Fill  the 8-inch dropper with standard potassium iodate-iodide reagent from the stock bottle by sucking it up with the rubber  bulb.  (The  dropper  must  be  kept  clean  and reserved for this test only.) 5.   Add the reagent to the mixture in the marked test tube, one drop at a time, counting the number of drops and stirring after each is added until a permanent blue color, which is not removed by stirring, is obtained. The standard   iodate-iodide   reagent   reacts   with   sodium sulfite  in  the  mixture,  and  the  formation  of  the permanent blue color from the action of excess reagent with the starch shows that the iodate-iodide reagent has consumed all the sodium sulfite in the mixture. 6.   Each drop of iodate-iodide reagent used (except the last one) indicates 5 ppm of sodium sulfite in the boiler  water  sample.    To  figure  the  concentration  of sodium  sulfite  in  the  boiler  water,  multiply  the  total number of drops of the standard iodate-iodide reagent used, less one, by 5. For example, when 5 drops were used, subtract 1 from 5 = 4, 5 x 4 = 20 ppm. 7.   Record the results of the test as ppm. Test for pH The value of pH indicates the degree of acidity or alkalinity  of  a  sample.  A  pH  of  7.0  represents  the neutral  point;  the  lesser  values  denote  acidity;  the greater  values  denote  alkalinity.  The  test  is  made  as soon  as  possible  after  you  take  the  sample.  Avoid exposure  to  the  air  as  much  as  possible  to  reduce absorption of CO₂. The following equipment is used in making the pH test of boiler water: One 2-oz bottle One 50-ml beaker Two vials of indicator paper, hydrions C pH 11 to 12 Two vials of indicator paper, hydrions pH 10 to 20 In  conducting  the  test  for  pH  of  boiler  water, remove a strip of pH 10 to 12 indicator paper from the vial and dip it into the sample in the beaker. Keep the paper immersed for 30 seconds; then remove it. When the sample does not change the color of the paper or colors it yellow or light orange, the pH of the sample is too low and the test is finished. When the paper turns orange or red, the pH is either satisfactory or too high. In that case, remove a strip of paper of pH 11 to 12 from the vial and dip it into the sample in the beaker. Keep the paper immersed for 30 seconds; then remove it. When the sample does not change the color of the paper or colors it a light blue, the pH is satisfactory. When the paper turns deep blue, the pH is higher than necessary. Blow down or reduce the dosage of caustic soda (NaOH). Test for pH of Treated Condensate In making a test for pH of treated condensate, take the sample from a point in the return piping near which condensation  takes  place,  such  as  after  a  trap,  or preferably where the return-line corrosion is known to occur. The sample must represent water flowing in the return  lines. Water  taken  from  the  return  tank, especially  of  large  installations,  generally  shows  a higher  pH.  A  sample  should  not  be  taken  from  a 1-33