M. Friedel 07i the Aldehydes and Acetones. 363 



the filtrate precipitated by acetate of lead. The precipitate, 

 which contains chromate of lead, is treated with nitric acid, 

 which, when dilute, only dissolves the organic salt. When this 

 liquid is three-fourths neutralized by ammonia, the salt precipi- 

 tates; when this precipitate is treated with sulphuretted hy- 

 drogen, and the liquid filtered, the acid is obtained in crystalline 

 plates on evaporating the solution. 



It forms large rhombic ciystals, which have a lamellar struc- 

 ture ; they arc soluble in water, with a strongly acid reaction 

 and odour. Heated to 100^ the acid loses water; at 140° it 

 melts, and boils at 150° C, disengaging carbonic acid, while 

 acetic acid distils over. Treated with sulphuric acid it is decom- 

 posed ; and it reduces chloride of gold. 



It forms with potash and ammonia neutral salts, which are 

 deliquescent, but crystallize in dry air. The corresponding acid 

 salts are readily obtained in large crystals. It precipitates lime, 

 baryta, and silver salts. 



Its analogies with oxalic acid are manifest. As the latter de- 

 composes into carbonic and formic acids, so malonic acid decom- 

 poses into acetic and carbonic acids. 



C4H2 08 = C2H2 0'» + 2C02. 

 Oxalic acid. Formic acid. 



C6H4 08=C'*H4 0-' + 2C02. 



Malonic acid. Acetic acid. 

 But it does not present with succinic acid, the next homologue, 

 that regular gradation of chemical functions which distinguishes 

 the true homologue. 



The aldehydes and acetones may be regarded, according to 

 Gerhardt and Chancel, as being formed on the type of hydrogen, 



TT y, — the general formula of an aldehyde being tt >, and of 



acetone y ^ > i'^ which X is a ternary oxygen radical, and Y an 



alcohol radical. Thus the aldehyde of acetic acid, C^ H"* 0^, is 



TT f , or Tt (■) "^ which an atom of hydrogen is replaced 



by the radical othyle; and the corresponding acetone, r^2 tj3 r, 



has the other atom of hydrogen replaced by methyle. A pow- 

 erful su])port for this view is found in the experiment of Wil- 

 liamson, who, by distilling a mixture of one atom valerianate of 

 potash with one atom acetate of potash, obtained a mixed acc- 



tone, ^2ji3 J- 



Friedel* has found that a mixed acetone is obtained by distil- 

 * Comptcs Rendus, vol. .xlv. p. 1013. 



