when using bouin solution, several potential problems can arise. due to the formalin in the solution, formalin pigment may be present when viewing tissue sections under the microscope. wet tissue should be fixed in bouin solution for less than 24 hours. excess picric acid should be washed out of tissue using several alcohol and water solutions or staining quality may deteriorate over time. wet tissue fixed in bouin solution should be stored in an alcohol and water solution rather than bouin solution. since bouin solution contains formaldehyde, picric acid and acetic acid, appropriate safety precautions for these substances should be taken and regulations followed. in particular, noting that picric acid can be explosive, sensitive to friction and shock when dry and in contact with some metals can form unstable metal picrates.