The following specifications will be employed for determining the suitability of cresylic disinfectant for use under the provisions of § 71.10(b)(3):

The product shall remain a uniform liquid when held at 0 °C. (32 °F.) for 3 hours (chill test).

The product shall dissolve completely in 30 parts of distilled water at 25 °C. (77 °F.) within 2 minutes (solution-rate test), producing a solution entirely free from globules and not more than faintly opalescent (solubility-degree test).

The product shall contain not more than 25 percent of inert ingredients (water and glycerin), not more excess alkali than the equivalent of 0.5 percent of sodium hydroxide, and not less than 21 percent of soap exclusive of water, glycerin, and excess alkali.

The product shall contain not less than 50 percent and not more than 53 percent of total phenols. It shall contain less than 5 percent of benzophenol (C 6H 5OH).

The methods of determining compliance with the specifications in paragraphs (a) to (d) of this section will be those described in United States Department of Agriculture Bulletin 1308, Chemical and Physical Methods for the Control of Saponified Cresol Solutions, so far as they are applicable.

Any suitable glyceride, fat acid, or resin acid may be used in preparing the soap, but not all are suitable nor are all grades of a single product equally suitable, Also various grades of commercial cresylic acid differ in suitability. Therefore, manufacturers are cautioned to prepare a trial laboratory batch from every set of ingredients and to prove its conformity with paragraphs (a) and (b) of this section, before proceeding with manufacture on a factory scale.