[Histonet] adjusting pH for formalin

[Vaughn Fierke]

Anyone with an idea to bring up the pH of 10% formalin to 7.0. Our
recycler tests 5 gallon batches at 6.2 and the paths would like
everything at 7.0. One source says add 1% sodium phosphate dibasic;
others say use SP dibasic saturated solution. Another source says that
using 1% sodium hydroxide is ok and won't alter fixation. Any consistent
suggestions?