66 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



acid rank as third and fourth from the bottom as the poorest solvents at 

 20°C. 



Another point which is of interest is that the ranking of the solvents for 

 the different acids varies with the temperature. Thus, glacial acetic acid and 

 methanol are among the poorest for stearic acid at 20°C. On the other 

 hand, at 60°C., as has been noted earlier, methanol and glacial acetic acid 

 have been found to be the two best solvents for stearic acid. Acetonitrile 

 and nitroethane are considered to be the poorest solvents throughout for 

 all acids at all temperatures. It is therefore evident that, in order to 

 specify the most satisfactory solvent for use, one must indicate not only 

 the fatty acid for which it is to be used but also the temperature at which the 

 extractions are to be made. 



c. Solubility of Saturated and Unsaturated Fatty Acids in Non- 

 aqueous Solvents at Low Temperatures. The comparative solubilities of 

 saturated and unsaturated acids in a number of solvents at temperatures 

 as low as — 70°C. have been studied extensively by Foreman and Brown. -'^^ 

 The results indicate that the solubility of linoleic acid exceeds that of 

 oleic acid, which in turn exceeds that of the next higher monoethenoid 



Table 28. Solubility Ratios of Oleic to Palmitic Aciu or Linoleic to Oleic Aciu 

 IN Several Solvents at Low Temperatures" 



Ciraiiis acid dissolved per 100 grains Ratio: 



solution (2) to (3) 



Temp., or 



Solvent °C. Linoleic (1) Oleic (2) Palmitic (3) (1) to (2) 



Ethylidene dichlori(l(> -25 26 . 8 3 . 24 82 . 7 : 1 



Methyl acetate -25 10.0 0.74 14.7:1 



Acetone -30 14.2 0.48 30.0:1 



Methanol -30 7.08 0.20 35.4:1 



Butanol -25 62.8 1.32 47.6:1 



Skellysolve B -30 11.8 0.0'J 131.1:1 



Carbon disulfide -30 15.7 <0.1 > 157.0:1 



Toluene -30 50.2 <0.] >500.0:1 



Ethyl ether -40 43.7 <0.1 >450.0:1 



Skellysolve B -70 0.60 0.24 2.5:1 



Carbon disulfide -62 4.12 0.398 10.3:1 



Methanol -70 3.94 0.32 12.3:1 



Acetone -70 5.19 0.40 13.0:1 



« H. D. Foreman and J. B. Brown, Oil & Soap, 21, 183-187 (1944). 



acid, eicosenoic acid. The solubility of the latter acid exceeds that of the 

 saturated Ch acid, myristic acid, and in some cases of the C12 saturated 

 acid (lauric acid). However, these solubility ratios vary somewhat accord- 

 ing to the solvent employed, as indicated in Table 28. The results on 

 Skellysolve B, methanol, and acetone are illustrated in Figures 7 to 9. 



"^ H. D. Foreman and J. B. Brown, Oil & Soap, 21, 183-187 (1944). 



