6 ACETIC ACID 



Which numbers closely agree with those obtained by Dr. Ure 



Acetic acid was formerly (and is still by some chemists) viewed as the hydrated 

 teroxide of a radical, Acetyl. (C 4 H s ) s , HO 



Acetyl. 



And therefore an anhydrous acetic acid, C 4 H 3 s , was supposed to exist. Many 

 attempts have been made to isolate this anhydrous acetic acid O 4 H 3 O 3 ; and a body 

 which has received this name has been obtained by Gerhardt, 1 by the double decom- 

 position of chloride of ncetyl and an alkaline acetate, thus 



CH S (0 2 C1) + KO.C 4 B? s = C"H a 8 + K Cl 



C H 3 OC1 + 2CC H n O = C 'H O ' + KC1 



This body Gerhardt describes as a colourless liquid having a strong smell of acetic 

 acid, but associated with the flavour of hawthorn blossom, having a specific gravity 

 of 1-073, and boiling at 137 C. (278 F.) ; falling in water in the form of oily drops", 

 only dissolving on gently heating that fluid. It is, however, not anhydrous acetic 

 acid, but a compound isomeric with the hypothetical anhydrous acetic acid C 4 H 3 s , 

 containing, in fact, double the amount of matter, its formula being C 8 H 8 s . See 

 ISOMEEISM. 



The impure varieties of acetic acid known as vinegar, pyroligneous acid, &c., are 

 the products met with in commerce, and therefore those require more minute de- 

 scription in this work. 



Before describing the manufacture of these commercial articles, it may bo in- 

 teresting to allude to a method of oxidising alcohol by means of spongy platinum ; 

 which may yet meet with extensive practical application. It is a well-known fact 

 that spongy platinum (e.g. platinum black), from its minute state of division, condenses 

 the oxygen of the air within its pores ; consequently, when the vapour of alcohol 

 comes in contact with this body, a supply of oxygen in a concentrated state is pre- 

 sented to it, and the platinum, without losing any of its properties, effects the 

 combination between the oxygen and the alcohol, converting the latter into acetic 

 acid. 



This may be illustrated by a very simple experiment. Place recently ignited 

 spongy platinum, loosely distributed on a platinum-gauze, at a short distance over a 

 saucer containing warm alcohol, the whole standing under a boll-glass supported by 

 wedges on a glass dish, so that on removing the stopper from the bell-glass a slow 

 current of air circulates through the apparatus ; the spongy platinum soon begins to 

 glow, in consequence of the combustion going on upon its surface, and acetic acid 

 vapours are abundantly produced, which condense and run down the sides of the 

 glass. The simultaneous formation of aldehyde is, at the same time, abundantly 

 proved by ite peculiar odour. 



In Germany this method has been actually carried out on the large scale, and, if it 

 wore not for the high price of platinum and the heavy duty on alcohol, it might be 

 extensively employed in this country on account of its elegance and extreme simpli- 

 city. See A.CETAL. 



1 Comptes Bcndus, xxxlv. 755. 



