ACETYL VALUE 33 



(4) The Reich ert Meissl Value. 



This represents the number of cubic centimetres of N/IO 

 caustic potash required for neutralizing the volatile acids liber- 

 ated from 5 grams of a sample of fat under certain special 

 conditions. 



The determination is carried out as follows : Five grams 

 of the sample are weighed into a 200 c.c. flask and saponified 

 by warming with 70 c.c. of 10 per cent alcohol and 2 grams 

 of caustic potash. The excess of alcohol is then evaporated 

 off and the residue, after dissolving in 100 c.c. of water, is 

 acidified with 40 c.c. of sulphuric acid (i : 10); a few chips of 

 asbestos are then dropped into the flask and the liquid is dis- 

 tilled through a Liebig condenser at such a rate that exactly 

 1 10 c.c. of distillate pass over in an hour. 100 c.c. of the 

 distillate remaining after filtration are titrated with N/iO caustic 

 potash in the presence of phenolphthalein. Appended are the 

 numbers obtained for several different fats : — 



Palm-kernel oil 5-6-8 Lard . o-68 



Coco-nut oil . e-e-yo Tallow . o'5 



Linseed oil . o'O Goose fat o-2-o'3 



Olive oil . 0-6 Butter fat 20-6-33-i 



The determination of the Reichert Meissl value is of 

 considerable value for the detection of adulteration in butter, 

 since any adulterant will at once lower the value. 



(5) The Acetyl Value. 

 This is a measure of the amount of hydroxyl groups which 

 a fat contains ; its value depends upon the fact that compounds 

 containing an alcoholic hydroxyl group react with acetyl 

 chloride or acetic anhydride so as to replace the hydrogen of 

 the hydroxyl by the acetyl group (CH3CO-) as shown oy 

 the equation : — 



ROH + ch'co>° = ROCOCH3 -f CH3COOH 



If the resulting acetyl derivative is saponified by means of 

 caustic potash it breaks up as follows : — 



ROCOCH3 + KOH = ROH -f CH3COOK 



and it is possible to determine the number of milligrams of 



3 



