As used in this article, “Reichert-Meissl number” means the number of milliliters of decinormal alkali which are required to neutralize the acidity of the distillate from five grams of fat treated in the manner specified in the regulations adopted by the director. Such regulations shall conform as closely as possible to the methods which are described in the book, entitled “Official and Tentative Methods of Analysis of the Association of Official Analytical Chemists,” published from time to time by that association.