SAPONIFICATION EQUIVALENT. 255 



centimetres of normal acid, the definition of a normal solution 

 being that it contains, or is equivalent to, in 1 litre a weight 

 in grammes equal to the equivalent of a substance. It is, there- 

 fore, necessary to calculate the weight of fat which would be 

 saponified by alkali equal to 1 litre of normal hydrochloric acid. 



Let W = the weight of fat taken. 



And V = the number of cubic centimetres of semi-normal 

 hydrochloric acid equivalent to the alkali required for saponifi- 

 cation. Then the saponification equivalent is expressed by 



2,000 W 



The relation between " potash absorption " (K) and " saponi- 

 fication equivalent " (S) is expressed by the formula 



56,100 

 HE"-' 



Instead of a pipette, the alcoholic alkali may be measured 

 from a burette or automatic measuring apparatus, and the 

 saponification may be conducted in a closed flask. An open 

 flask or basin should not be used, as ethyl butyrate, an inter- 

 mediate product of saponification (p. 12), is volatile ; this would 

 cause a low value to be obtained. 



According to Kcettstorfer, the potash absorption varies from 

 221-5 to 233-0 in genuine butters, with an average of 227-0. 

 His experience has been confirmed by numerous observers, 

 and the limits have been extended 218 to 235. The saponifi- 

 cation equivalent varies from 253-3 to 240-8, the average being 

 247-1. 



Other oils and fats have a potash absorption of 190 to 199, 

 with an average of about 195 ; or a saponification equivalent 

 of 295-3 to 282-0, with a mean of 287-6. 



Coconut and palm-nut oils yield, however, figures which are 

 very different, 246-2 to 268-4. 



Estimation of the Baryta Value Avd-Lallemant's Method. 

 Two grammes of butter fat are saponified as in the Kcettstorfer 

 process, and the solution after neutralisation is evaporated to 

 dryness, 10 c.c. of water is added, and the evaporation con- 

 tinued to remove the last traces of alcohol. The residue is 

 dissolved in boiling water, and the solution, which should measure 

 about 180 c.c., poured into a 250 c.c. flask. The flask is placed 



N 



on a boiling water-bath, and 50 c.c. of barium chloride solution 



o 



are added, with constant shaking. After standing on the water- 

 bath for fifteen minutes, the solution is cooled, and made up 

 to 250 c.c. The solution is filtered, the first portions being 



