90 PROPIONIC ACID. 



bolic solution of potassa, evaporating, and distilling the 

 residue with sulphuric acid. 



Properties. Colorless, clear liquid, with an odor 

 resembling that of acetic acid; specific gravity, 0.992 

 at 18 ; boiling point, 139. Mixes with water in all 

 proportions, can be separated from this solution by 

 means of calcium chloride. 



Its salts are all soluble in water. 



The silver salt, C 3 H 5 2 Ag, crystallizes in small needles, 

 which are difficultly soluble in cold water. 



Ethyl propionate, C 3 H 5 O.O.C 2 H 5 . Is prepared like 

 acetic ether. Colorless liquid, boiling at 100. 



Substitution-products of propionic acid. Of 



each of the simple substitution-products, formed by the 

 displacement of one hydrogen atom by a monovalent 

 element or a monovalent group, two varieties can exist. 

 Their difference results from the difference in position 

 of the substituted hydrogen atoms ; it being in the one 

 case in the group CH 3 , in the other in the centre group 

 CH 2 . The direct action of chlorine, etc., appears only 

 to cause the substitution of hydrogen, that is in com- 

 bination with the central carbon atom. 



a-Chlorpropionic acid, C 3 H 5 C10 2 = CIP.CHCl.CO. 

 OH. Is prepared by the decomposition of lactyl chloride 

 (see Lactic Acid) with water. Colorless liquid, boiling 

 at 186 ; specific gravity, 1.28. The ethyl ether of this 

 acid 8 H 5 CiaQ.(?H is obtained by bringing lactyl 

 chloride together with alcohol, and by the action of 

 phosphorus terchloride on lactic ether. Liquid, boilino- 

 at 144. 



/3-Chlorpropionic acid, C 3 H 5 C10 2 =CH 2 C1.CH 2 .CO, 

 OH. The crystalline chloride of this acid (C 3 H 5 O.C10.C1) 

 is formed by the action of 3 molecules phosphorus 

 pentachloride on lead gly cerate or glyceric acid. Yields 

 with alcohol ethyl &-chlorpropionate C 3 H 5 C10.0.C 2 IP, a 

 liquid that boils at 150-160. From this is obtained 

 the free acid by treating with baryta water, and deconi- 



