Mary:
  Formalin pigment, also known as "hematin", has been found in tissues stored in
  formalin for long periods of time since formalin began to be used,
  Hematin which, as you know, is a dark brown, microcrystaline and iron-negative pigment also develops in Bouin's fixed tissue, specially in spleen, heart and almost any blood rich tissue.
  It was so frequent years ago than it lead to the development of neutral buffered formalin (NBF) or formalin containing enough salts to allow the pH to remain neutral (buffered) after long periods of time.
  You can use a pH indicator paper strip because you only want to determine if the
  formalin is acid (less than pH 7) or not. You don't want to determine the exact pH for which you will need a calibrated pH-meter.
  On the other hand there are good pH paper strips like one called "pHydrion Vivid 6-8" that will tell you the pH from values of 6.0 to 8.0 in increments of 0.2 to 0.4 units.
  Another pH strips called "color pHast" determine pH range from "0" to "14" in pH 1 unit increments.
  I hope this will help you!
  René J.

MARY JOHNSON  wrote:
  hi histonette, I am having problems with formalin pigments, I am sure it is because of the out dated Formaldehyde that the moruge is using. Can any one help me prove this 
what test can i use? Is the paper pH ok to prove this. I need help with this one
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