ELECTROLYTIC SYNTHESIS OF DIBASIC ACIDS. 371 



The acid remaining after distilling off the ether had, when warmed, a pungent odour, 

 and its solution in bisulphide of carbon at once, at ordinary temperature, decolorised a 

 solution of bromine in the same solvent. An attempt was made to distil some of the 

 acid under atmospheric pressure, but when the temperature had risen to a little over 

 130°, the acid suddenly changed, with evolution of heat, into a white amorphous solid. 

 This substance agrees in all respects with the description given by Fittig and Engel- 

 hokn * of the polymeric form of methylacrjdic acid. It swells up in water, and appears 

 to dissolve gradually. This is, however, not the case, as what looks like a perfectly clear 

 solution cannot be filtered. On adding mineral acid to the apparent solution, the acid 

 separates as a white flocculent precipitate. The substance dissolves in ammonia, and the 

 solution gives precipitates with the chlorides of barium and calcium. 



A combustion of the polymeric acid, dried at 130°-135°, gave the following numbers : — 

 01396 gramme gave 0*2846 gramme C0 2 , and - 0881 gramme H 2 0. 

 Calculated for (C 4 H 6 2 )„. Found. 



C 5581 55-60 



H 6-97 7-01 



The composition is therefore that of methylacrylic acid. 



Another portion of the original acid was converted into the potassium salt. This 

 was recrystallised from hot alcohol, from which it separates in fine scales. 

 0-2895 gramme of the potassium salt gave - 2024 gramme of K 2 S0 4 . 

 Calculated for C 4 H 5 2 K. Found. 



K 315 31-4 



The free acid solidified when cooled to 0°, and fused again at 1 4°. 



The fusing-point of methylacrylic acid is 16°. 



It is worthy of note, that the smell of the methylacrylic ether produced by electro- 

 lytic synthesis is not unpleasant, but rather resembles that of the ethers of the saturated 

 monobasic acids. The ether prepared by Frankland and Duppa's method has been 

 described by all observers as having a disagreeable smell. 



Ethylcrotonic Acid. — Of about 80 grammes of ethereal product distilling below 230 c , 

 obtained by electrolysing ethyl-potassium diethylmalonate, 45 grammes boiled between 

 150° and 170°. This fraction was saponified by means of 20 grammes of caustic potash 

 in alcoholic solution, and the acid was separated in the usual way. The liquid acid thus 

 obtained boiled without decomposition at 204°-206° C. (uncorrected). The boiling-point 

 of ethylcrotonic acid is 209°. In order to purify it, it was distilled with steam and then 

 converted into the calcium salt by boiling with water and calcium carbonate. The 

 calcium salt crystallised from water in beautiful shining needles. 



0-3133 gramme of the air-dried salt lost 00797 gramme at 120°, and gave 01178 gramme of CaS0 4 . 



Calculated for Ca(C 6 H 9 2 ) 2) 5H 2 0. Found. 



Ca . . . 11-24 11-06 



H 2 . . . 25-29 2543 



* Liebig's Annalen 200, 70. 



