20 



small to weigh with any degree of accuracy. This repre- 

 sents the volatile constituent. 



The remaining mass was redissolved in alcohol and 

 made slightly neutral by adding potassium alcoholate, 

 using phenolphthalein as indicator. The so3.ution was 

 diluted with distilled water to about 100 cc. 30 cc. of 

 a ten per cent solution of lead acetate was diluted to 

 150 cc. with water and boiled. The hot solution was run 

 into the soap solution, constantly shaking the latter so 

 that the lead soaps would adhere to the sides of the 

 flask. The flask was then filled with hot water and then 

 allowed to cool. The lead salts all adhered to the 

 glass, leaving a clear supernatant fluid which was de- 

 canted off. The soap was then shaken up with ether at 

 37C. The ethereal solution was then cooled and filtered. 

 The filtrate contains the lead salts of the liquid fatty 

 acids. This filtrate was then shaken with twenty per 

 cent hydrochloric acid, to decompose the lead salts. As 

 the fatty acids are set free from the lead salts, they 

 are taken up by the ether. The ethereal layer was re- 

 moved; washed with water until the washings were free 

 from acid; and the ether then evaporated. The remaining 

 liquid fatty acid weighed 1.021 gram. This acid solidi- 

 fied when cooled on ice and melted at 13C. The neutra- 

 lization value was then found as follows: 1.021 grams 

 were neutralized by 34.9 cc. of N/10 KOH. This is equiva- 

 lent to 34.1 cc. per gram of acid, or 191 grams KOH. The 

 neutralized acids were now acidified with 20% hydro- 

 chloric acid and shaken out with ether. The ether was 

 then evaporated and the iodine value was obtained as 

 follows (Hubb's process): 



The iodine solution is prepared by dissolving 13.5 

 grams iodine in 250 cc. of 95$ alcohol, and by dissolving 

 15 grams of mercuric chloride in 250 cc. of 95$ alcohol 

 and mixing these two solutions. A standardized solution 

 of sodium thiosulphate was prepared by dissolving 24 

 grams of the salt in one liter of water. 0.2 gram of 

 iodine and 1.0 gram of potassium iodide are dissolved in 

 about 50 cc. of water. This solution is titrated to 

 neutrality by the thiosulphate solution, using starch 

 solution as indicator. It was found that 15,4 cc . of thi- 

 sulphate solution was equivalent to 0.2 gram of iodine. 

 The 1.021 gram of fatty acid is dissolved in 10 cc. of 

 chloroform and 50 cc. of iodine solution added. The 

 solution was allowed to stand for fifteen hours. 20 cc. 

 of 10$ potassium iodide solution was added, and the 

 volume made up to 500 cc. with water. This solution was 

 then titrated with the thiosulphate solution. It was 



