Mr Fenton, Soluble forms of metallic dihydroxy tartrates. 73 



Soluble forms of metallic dihydroxytartrates. By H. J. H. 

 Fenton, M.A., F.R.S., Christ's College. 



[Read 27 February 1905.] 



Sodium dihydroxytartrate was first obtained by Griiber in 

 1879 and was afterwards further examined by Kekule and by 

 Barth. The barium salt was also prepared by Barth and in 1889 

 Miller succeeded in isolating the free acid. The author in 1898 

 discovered a new and simple method for preparing the free acid 

 in a pure state and made a further study of its relationships ; the 

 lithium, potassium, rubidium, caesium, and ammonium salts were 

 also prepared and analysed. 



From the fact that the sodium salt decomposes on heating into 

 sodium tartronate and carbon dioxide, Griiber concluded that 

 the acid should be regarded as tribasic carboxytartronic acid 

 C (OH) (COOH) 3 and this view of its constitution appeared to be 

 borne out by Barth's analysis of the barium salt ; in this case 

 the sodium salt would have to be considered as a basic salt. 

 Kekule's experiments however shewed conclusively that the acid 

 is really dibasic and this result was further established by the 

 author's experiments on the titration of the free acid and analyses 

 of the salts above mentioned. The basicity of the acid and com- 

 position of its salts are therefore quite in harmony with Kekule's 

 formula which represents the acid as 



COOH . C (OH), . C (OH) 2 . COOH 



or tetrahydroxy-succinic acid. 



Although this formula is now very generally accepted it cannot 

 be considered as entirely established ; the comparative stability of 

 the free acid on heating and the decomposition into tartronic acid 

 and carbon dioxide when its aqueous solution is boiled are pro- 

 perties which at first sight appear to be hardly consistent with 

 such a constitution. 



Compare Griiber, Ber. 1879 (12) 514; Barth, Sitz. Acad. Wien, 

 82, ii. 1024. 



Fenton, Trans. Chem. Soc. 1898 (73) 71, 167 and 472. 



Debus, Trans. Chem. Soc. 1904 (85) 1388. 



Investigations are now being undertaken with the object of 



6—2 



