326 CONSIDERATION OF CARBON COMPOUNDS. 



It is also a product of the decomposition of sugar, starch, etc. 

 Formic acid is a colorless liquid having a penetrating odor, and a 

 strongly acid taste ; it produces blisters on the skin ; it is a powerful 

 deoxidizer, being, when thus acting, converted into carbon dioxide 



and water : 



CH 2 2 + O = CO 2 + H 2 0. 



Acetic acid, H.C 2 H 3 O 2 , or C 2 H 3 O.OH, or CH 3 .CO 2 H 60. 

 The most important alcohol is ethyl alcohol, and the most largely 

 used organic acid is acetic acid, obtained from ethyl alcohol by oxi- 

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

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



Acetic acid is formed chiefly either by the oxidation of alcohol 

 (and aldehyde) or by the destructive distillation of wood. It is pi 

 duced commercially on a large scale as follows : A diluted ale 

 (8 to 10 per cent.) is allowed to trickle down slowrV through 

 shavings contained in high casks having ne^brate^v sides in/order to 

 allow a free circulation of the aJfVvthe^.tynpera^eKsVkyt at about 

 24 to 30 C. (75 to 86 F.), arid 4lk4iqi^NSavin^^d through 

 the shavings is repeatedly poured back in order tofcause 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, whilst acetic acid 

 distils over. 



Experiment 46. Add to 54 grammes of sodium acetate contained in a small 

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



