Organic analysis

1915 The Analyst  
1915, 7, 30-34.)-The author discusses the influence of laotone-forming hydroxy acids (more particularly the y-acids) on estimations of the acid, saponification, and acetyl values of fatty acids. For instance, if one-half of a sample of hydroxystearic acid should undergo lactonisation, the acid value would be depressed from 186.85 to 96.31, and the saponification value increased from 186-85 to 192.62, whilst the ester value would become 96.31 instead of zero. When a difference between the acid
more » ... 7 Zanzibar Copal. Madagascar Copal. and saponification values shows that lectones are present in a fatty acid, the mean molecular weight (m) of the fatty acids before lactone formation may be Demerara Copal. calculated by the formula : m= %lo8+ 18' 016 (' -' ), where a is the acid value and S s the saponification value of the mixed fatty acids. Since lactones in a mixture of fatty acids are derived from pre-existing hydroxy acids, the acetyl value of Benedikt-Ulzer (ester value of the acetylated acids) is a truer measure of the original hydroxyl content of fatty acids than the acetyl number of Lewkowitsch. (potassium hydroxide required to saponify the combined acetyl in the acetylated acids). Thus, y-hydroxystearic acid in the glyceride molecule can be acetylated, and would show an acetyl number by Lewkowitsch's method ; whereas the separated fatty acids would show no acetyl value on account of the formation of stearo-lactone. The original acetyl value, calculated to the acetylated hydroxy acids before lactone formation, may be found from the formula, : + 0 , 0 0~0 7~c -%), where r is the acetyl ester value (Benedikt-Ulzer) and ( the acetyl value (Lewkowitsch). w. P. s.
doi:10.1039/an915400156b fatcat:77tp4dc4zzfuzctcrt4eatgmme