MONOBASIC FATTY ACIDS. 501 



dation. Acetic acid is found in combination with alkali metals in 

 the juices of many plants, also in the secretions of some glands, etc. 



There are many reactions by which acetic acid can be obtained 

 similar to formic acid. For all practical purposes, however, it is 

 made either by the oxidation of alcohol (and aldehyde) or by the 

 destructive distillation of wood. It is produced commercially on a 

 large scale as follows : A diluted alcohol (8 to 10 per cent.) is allowed 

 to trickle down slowly through wood shavings contained in high 

 casks having perforated sides in order to allow a free circulation of 

 the air ; the temperature is kept at about 24 to 30 C. (75 to 86 

 F.), and the liquid having passed through the shavings is repeatedly 

 poured back in order to cause complete oxidation. When the latter 

 object has been accomplished the liquid is a diluted acetic acid. 



It appears that the conversion of alcohol into acetic acid is greatly 

 facilitated by the presence of a microscopic organism (mycoderma 

 aceti) commonly termed " mother of vinegar." This serves in some 

 unexplained way to convey the atmospheric oxygen to the alcohol. 

 The term " acetic fermentation " is often applied to this conversion, 

 although it is not a true fermentation, since no splitting up of the 

 alcohol molecule into other less complex compounds, but a process of 

 slow oxidation, takes place. 



The second process for manufacturing acetic acid is the heating of 

 wood to a red heat in iron retorts, when numerous products (gases, 

 aqueous and tarry substances) are formed. The aqueous products 

 contain, besides other substances, methyl alcohol and acetic acid. 

 The liquid is neutralized with calcium hydroxide and distilled, when 

 methyl alcohol, water, etc., evaporate and a solid residue is left, which 

 is an impure calcium acetate. From this latter, acetic acid is obtained 

 by distilling with sulphuric (or hydrochloric) acid, calcium sulphate 

 (or chloride) being formed and left in the retort, while acetic acid 

 distils over. 



Experiment 57. Add to 54 grammes of sodium acetate contained in a small 

 flask which is connected with a Liebig's condenser, 40 grammes of sulphuric 

 acid. Apply heat and distil over about 35 c.c. ' Determine volumetrically the 

 amount of pure acetic acid in this liquid. 



Pure acetic acid, or glacial acetic acid, is solid at or below 15 C. 

 (59 F.); at higher temperatures it is a colorless liquid having a 

 characteristic, penetrating odor, boiling at 118 C. (244.4 F.), and 

 causing blisters on the skin ; its specific gravity is 1.049 at 25 C. ; 

 it is miscible with water, alcohol, and ether, is strongly acid, forming 

 salts known as acetates, which are all soluble in water. 



