Marsh gas type

Kekule paved the way for this paper a year earlier, when he added a fifth type to Gerhardt s four. The new type involved the combination of four atoms or radicals with carbon. Because the simplest molecule of this type is methane or marsh gas, CH4, it was known as the marsh gas type. Kekule also insisted that his types were not merely characterized by similarity of formula and prop-... 

The last formula—a stable compound, not a radical—is that of marsh gas, today known as methane. Some, following Anschutz, have imder-standably seen in this paper the proposal of a fifth chemical "type" to add to Gerhardt s four, namely the "marsh gas type," and a modern chemical eye sees an implicit suggestion of carbon tetravalence here. 

In proposing this "marsh gas type," Kekule was doubtless carrying further the suggestions of William Odling s March 1855 paper on hydrocarbon radicals. But the predecessor whom Kekule explicitly named was not the atomic skeptic Odling, nor Gerhardt, but rather Dumas, who in 1840 had published a table similar to Kekule s, headed by a formula for marsh gas. Choosing his words carefully, Kekule stated that he was... 

What is sometimes called the Older Type Theory of Dumas (p. 364) was not in itself of very much importance. It was the researches of Hofmann on the Ammonia Type and those of Williamson on the Water Type, both published in England about 1850, which paved the way to the enunciation by Gerhardt of the Newer Type Theory in 1853, completed by the addition of the fourth marsh gas type by Kekule in 1857. The newer type theory had a great influence on the development of chemical theory. The new organic chemistry begun by Dumas was markedly advanced by the researches of Laurent and Gerhardt, and the theoretical conclusions they drew from them. We turn now to a consideration of these. It was only later, in the work of Kolbe, that the useful parts of Berzelius s then discredited theory received a new life. 

He does not emphasise the importance of this fourth (marsh gas) type nor extend it to a number of compounds (as Kekule did later, see p. 535). In his lecture, Odling favoured the etherin rather than the ethyl theory. 

Kekule only twice gives a marsh gas type, the same in both, prussic acid. ... 

Kekule s indebtedness to Odling, who had virtually used the marsh gas type in 1855 (see p. 464) and with whom Kekul6 was acquainted in London, is very probable. ... 

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