1420 FOODS AND FOOD ADULTERANTS. 



gram of sodium hydroxid and neutralizes 0.0088 gram of butyric 

 acid (C 4 H 8 O 2 ). 



Alcoholic potash solution. Dissolve 40 grams of good potassium 

 hydroxid in 1 liter of 95 per cent alcohol that has been boiled for 

 2 days with potassium hydroxid in a flask with reflux condenser 

 attached, and redistilled. The solution must be clear and the potas- 

 sium hydroxid free from carbonates. 



Standard acid solution. Prepare accurately a half normal solution 

 of hydrochloric acid. 



Indicator. Dissolve 1 gram of phenolphthalein in 100 cc of 95 



per cent alcohol. 



WEIGHING OP SAMPLE. 



The saponification is carried on in a wide-mouth Erlenmeyer flask 

 holding from 250 to 300 cc. These are cleaned by thoroughly wash- 

 ing with water, alcohol, and ether, wiped perfectly dry on the outside, 

 and heated for one hour at the temperature of boiling water. The 

 flasks are then placed on a tray, covered with a silk handkerchief, and 

 allowed to cool. They must not be wiped with a silk handkerchief 

 within fifteen or twenty minutes of the time they are weighed. 



About 5 grams of the melted fat, which has been filtered, is run in 

 by means of a pipette, and after cooling the flask and contents are 

 again weighed. 



KOETSTORFER OR SAPONIFICATION NUMBER. a 



Measure 50 cc of the alcoholic potash solution into the flask by 

 means of a burette or pipette, which is allowed to drain a definite time. 

 Connect the flask with a reflux condenser and boil for thirty minutes, 

 when the fat is completely saponified. Cool the flask and titrate with 

 half normal hydrochloric acid, using phenolphthalein as indicator. 

 The Koetstorfer number (milligrams of potassium hydroxid required 

 to saponify 1 gram of fat) is obtained by subtracting the number of 

 cubic centimeters of lydrochloric acid used to neutralize the excess of 

 alkali after saponification from number of cubic centimeters necessary 

 to neutralize the 50 cc of alkali added, multiplying the result by 28.06 

 (milligrams potassium hydroxid per cubic centimeter) and dividing by 

 the number of grams of fat used. 



To calculate the saponification equivalent a divide 56,100 by the 

 saponification number, the saponification equivalent being the number 

 of grams of fat saponified by one equivalent of potassium hydroxid, 

 or 56.1 grams. There is no advantage in stating it in this way, and 

 for sake of uniformity the Koetstorfer number being more generally 

 used, it would seem advisable to adopt it. 



a Chiefly of value in oil work in the detection of rape oil, resin oil, and paraffin 

 products. 



b Allen, Com. Org. Anal., 3d ed., vol. 2, pt. 1, pp. 53-55. 



