124 ANGELIC ACID. 



with 1 molecule bromine ; and is converted into butyric 

 acid by the action of sodium amalgam and water. 



2. Isocrotonic acid, CH 3 .CH:CH.CO.OH. Is ob- 

 tained by the action of sodium amalgam on chloriso- 

 crotonic acid. Colorless liquid: boils at 172; does 

 not congeal at 15. 



Chlorisocrotonic acid, C 4 H 5 C10 2 . Is formed from 

 acetylacetic ether together with chlorcrotonic acid. 

 Colorless crystals, difficultly soluble in water. Sub- 

 limes at the ordinary temperature. Fusing point, 

 59.5 ; boiling point, 195. 



3. Methacrylic acid, CH 2 :C j QQQ H The ether of 



this acid, C 4 H 5 O.O.C 2 H 5 , is produced by the action of 

 phosphorus terchloride on ethyl isoxybutyrate. The 

 free acid is liquid, does not congeal at 0, and is resolved 

 into formic and propionic acids by fusing with caustic 

 potassa. 



3. Angelic Add. 

 C 5 H 8 2 = C 4 H 7 .CO.OH. 



Occurrence and preparation. In the roots of Angelica 

 archangelica. In order to prepare the acid from these, 

 they are boiled with lime, filtered, the filtrate decom- 

 posed by sulphuric acid, and distilled ; the distillate 

 saturated with sodium carbonate, evaporated to dry- 

 ness, and the residue again distilled with sulphuric 

 acid. Acetic, valeric, and angelic acids pass over; by 

 means of cooling, the latter separates from the mixture 

 in crystalline form. It is also produced by the action 

 of caustic potassa on the essential oil of chamomile 

 (volatile oil of Anthemis nobilis), which appears to con- 

 tain an ether of angelic acid; and by heating laserpi- 

 tium and peucedanin with an alcoholic solution of 

 potassa. 



Properties. Colorless needles, fusing at 45, but 



