Allow the flask to cool somewhat, and through the condenser tube add 50 cc. of distilled water free from carbon dioxide at a temperature of about 80deg. C., taking care that the flask is not loosened from the condenser. The object of cooling is to avoid any sudden rush of vapors from the flask on adding water, and to avoid breaking the flask. Time is saved by adding the water before the contents of the flask solidify, but the contents may be allowed to solidify and the test proceeded with the next day without detriment, bearing in mind that the anhydride in excess is much more effectively hydrolyzed in hot than in cold water. The contents of the flask may be warmed to, but must not exceed, 80deg. C., until the solution is complete, except a few dark flocks representing organic impurities in the crude. By giving the flask a rotary motion, solution is more quickly effected. Cool the flask and contents without loosening from the condenser. When quite cold wash down the inside of the condenser tube, detach the flask, wash off the stopper or ground glass connection into the flask, and filter the contents through an acid-washed filter into a Jena glass flask of about 1 litre capacity. Wash thoroughly with cold distilled water free from carbon dioxide. Add 2 cc. of phenolphthalein solution (_F_), then run in caustic soda solution (_C_) or (_D_) until a faint pinkish yellow color appears throughout the solution. This neutralization must be done most carefully; the alkali should be run down the sides of the flask, the contents of which are kept rapidly swirling with occasional agitation or change of motion until the solution is nearly neutralized, as indicated by the slower disappearance of the color developed locally by the alkali running into the mixture. When this point is reached the sides of the flask are washed down with carbon dioxide-free water and the alkali subsequently added drop by drop, mixing after each drop until the desired tint is obtained. Now run in from a burette 50 cc. or a calculated excess of _N_/1 NaOH (_D_) and note carefully the exact amount. Boil gently for 15 minutes, the flask being fitted with a glass tube acting as a partial condenser. Cool as quickly as possible and titrate the excess of NaOH with _N_/1 acid (_E_) until the pinkish yellow or chosen end-point color just remains.[21] A further addition of the indicator at this point will cause an increase of the pink color; this must be neglected, and the first end-point taken. From the _N_/1 NaOH consumed calculate the percentage of glycerol (including acetylizable impurities) after making the correction for the blank test described below. 1 cc. _N_/1 NaOH = 0.03069 gram glycerol. The coefficient of expansion for normal solutions is 0.00033 per cc. for each degree centigrade. A correction should be made on this account if necessary.