Pyro tartaric acid

Mono-methyl succinic acid is known also as pyro-tartaric acid as it is... 

Succinic acid Mono-methyl succinic acid Pyro-tartaric acid 1... 

This new acid, isomeric with mono-methyl succinic acid, pyro-tartaric acid, is known as glutaric acid, or systematically, as 1-5-pen-tan-di-oic acid. 

Tt is to be expected, however, that the bodies I and IV together, and the bodies V and VI together, will be practically identical. (The formulae are misprinted in the paper.) He also gives formulae for succinic acid (a), pyro-tartaric acid (jS) and diglycollic acid (y) ... 

Kekule showed that itaconic and citraconic acids, and an isomer mesaconic acid obtained by J. Gottlieb by boiling citraconic acid with dilute nitric acid, are unsaturated when reduced with sodium amalgam they all form pyro-tartaric acid but with bromine they form three different dibromotartaric acids. He knew that they were methyl-substituted maleic or fumaric acids. R. Fittig, at the end of a long memoir on the unsaturated acids, remarked that no constitutional formulae exist which explain all the facts, if the dogma that in unsaturated compounds the carbon is always multiply linked is retained but he was unaware that two years before the whole problem had been solved, on the basis of a very simple assumption, by van t Hoff (see p. 757), and that of citraconic acid, etc., was cleared up on the same basis by Wislicenus (p. 762). 

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