Solutions containing 0.05 to 0.1% Ammonium Bifluoride are suitable for sufficient Ammonium Bifluoride solution has been added. A dry strip of solution of one pound per gallon (approximately 11%) may be prepared and paper is wetted with the neutralized solution; the color that develops immediately on the paper is compared with color standards that show the pH directly. this purpose. This is equivalent to approximately 1/2 to 1 pound of kept in polyethylene bottles, and diluted as needed. For best results, souring should be carried to a pH of 4,5-5.0 pHydrion papers, suitable for the pH range 3.0-5.5, available from ammonium Bifluoride per 100 gallons solution. for convenience, a stock scientific supply houses, may be used to check pH to assure that