Due to its extreme toxicity, low vapor pressure, and being a strong oxidizing agent, precautions are necessary for its handling. Properties Making it Useful in SEM Causes tissue hardening, imparting mechanical strength and affording some extra resistance to shrinkage and distortion during subsequent steps. Imparts a small measure of conductivity, which is useful in specimens with extremely detailed surfaces or with deep recesses such as the crypts between intestinal villi, which are not easily coated. Also serves as a mordant for some of the chemical coating deposition techniques which will be mentioned later. Picric acid is not itself coagulative, but precipitates proteins, rendering them insoluble without altering their structure.
Many labs routinely emloy it with aldehydes as a general purpose fixative.
It may be safely kept in the lab if kept wet. Buffer selection may be more critical than fixative selection. As pH is changed on either side, the capacity to hold pH steady is decreased. The pH range through which a buffer is effective, depends on the buffer. A buffer must be selected which is effective at the pH desired.