210 PEOCEEDINGS OP THE AMERICAN ACADEMY 



analyses of Hun a us, "Wallacli * had assigned to the barium salt of 

 the y8 dichloracrylic acid the formula Ba(C8HCl202)2 • SHgO, and to the 

 calcium salt the probable formula Ca(CoHCl202) . l^HjO ; while the 

 corresponding salts of our acid we had found to have the formulge 

 ■Ba(C3HCl202)2 . HgO and Ca(C3HC102)2 • SH^O. Although the po- 

 tassium salt of neither acid contained water of crystallization, one crys- 

 tallized in plates, the other in needles. 



Quite recently Wallach f has published the results of several deter- 

 minations made since the publication of a preliminary notice t of our 

 dichloraci'ylic acid. These determinations show that the formulas 

 which had previously been assigned to the barium and calcium salts of 

 his acid were incorrect, and that they probably each contained two 

 molecules of water. To these determinations, however, Wallach 

 would attach but little weight for the identification of the acid, 

 although he considers the isomerism of the two dichloracrylic acids 

 to be fully established. 



" Ich mochte aber nach den gemachten Erfahrungen diesen Bestim- 

 mungen vorliiufig keinen besonderen Werth fiir die Charakterisirung 

 der Dichloracrylsaure aus Chloralid beilegen. Man wird besser thun, 

 sich dafiir an die scharf bestimmbaren Eigenschaften der gemessenen 

 freien Saure und allenfalls an die tafelformige Ausbildung des was- 

 serfreien Kalisalzes, sowie an die angegebenen krystallographischen 

 Daten des Baryumsalzes, austatt an die bisher ausgefiihrten Wasser- 

 bestimmungen zu halten ; fiir letztere miissen noch weitere Versuche 

 vorbehalten bleiben. Jedenfalls muss aber der Zweck der obigen 

 Angaben jetzt schon als erreicht bezeichnet werden : namlich die 

 vollige VerscMedenheit der Dichloracrylsaure aus Chloralid der nur 

 die Foi-mel CCU^CH-COgH zukommen kann, von der, welche Ben- 

 nett und Hill aus 3fucochlor saure erhielten dejiniiiv zu bestdtigen." § 



Unfortunately we have as yet been unable to obtain either our 

 acid or its barium salt in a form which would admit of crystallographic 

 study. Still, the differences already established leave no reasonable 

 doubt that the two acids are isomeric, and the acid from mucochloric 

 acid may therefore be distinguished for convenience as the a dichlor- 

 acrylic acid. 



The behavior of this acid towards reagents has thus far been little 



* Ann. Cliem. u. Pharm., cxciii. 23. 



t Ibid., cciii. 83. 



} Berichte der deutsch. chem. Gesellsch., xii. 665. 



§ Loc. cit., p. 80. 



