Mar. is, 191S Fatty A cids in Butter I- at 727 



As an illustration of the method of calculation, take the fifth fraction 

 of a sample of butter fat (Table III) vv^hich weighed 50.69 gm., had a 

 saponification number of 219.280 and an iodin number of 14.055, and 

 was intended to contain ethyl laurate, myristate and oleate. 



The iodin number, convertible to ethyl oleate by the factor 1.22284, is 

 equivalent to 17.187 per cent. 



Then i.oo— 0.17187, or 0.82813, is the percentage of the residual esters 

 in the fraction and 2i'9.28o— (0.17187X 180.758), or 188.213, their alkali- 

 consuming power. The latter divided by the former gives a saponifica- 

 tion number of 227, a figure between that of ethyl laurate (245.771) and 

 that of ethyl myristate (218.885), ^-s anticipated. 



Let X indicate ethyl laurate and y ethyl myristate, then 



rc+r = 0.82813 

 245. 77ix+2i8.885>'= 188.213 



3;= 25.842 per cent of ethyl laurate 

 )/= 56.971 per cent of ethyl myristate. 



The percentages 0.25842, 0.56971, and 0.17187 multiplied by the 

 weight of the fraction (50.69 gm.), gives the weight of the several esters 

 in the fraction 13.099, 28.879, ^^^ 8.712, which by their respective fac- 

 tors 0.87717, 0.89060, and 0.90966 may be converted into the weight of 

 the several fatty acids in the fraction. The total weight of a fatty acid 

 divided by the weight of fat taken (300) gives the percentage of that 

 acid in the butter fat. The same method of calculation is followed in 

 each of the other fractions. 



METHOD IN DETAIL 



Reagents. — Alcohol : absolute. 



Hydrochloric acid : dry, generated by dropping concentrated sulphuric 

 acid into a mixture of concentrated hydrochloric acid and sodium chlorid 

 and dried by passing through concentrated sulphuric acid. 



Sulphuric acid: concentrated, heated to 225° C. 



Ethyl ether: anhydrous, freshly distilled over metalic sodium. 



Magnesium chlorid: dry powder, neutral. Dried at 75° to 80° C. 



Magnesium chlorid solution: 250 gm. of dry powder to 500 c. c. of 

 absolute alcohol. 



ESTERIFICATION AND PURIFICATION OF ESTERS. — Into a I,000-C. C. flat- 



bottom globe flask are brought 150 gm. of filtered fat, together with 

 400 c. c. of alcohol previously charged with 8 gm. of dry hydrochloric 

 acid, or 4 c. c. of concentrated sulphuric acid and a number (25) of glass 

 beads. The flask is connected with a long spiral or other form of reflux 

 condenser, and the mixture carefully boiled on 50-nicsh Nichrome wire 

 gauze lor 24 hours. 



