XX. 

 THEORY OF TYPES IN CHEMISTRY. 



(1848-1861.) 



In the years 1848 - 1854 1 published in the American Journal of Science several essays 

 on the theory of chemical types and on related questions in the science. The first, on 

 the Anomalies' in the Atomic Volumes of Sulphur and Nitrogen and on Chemical Classi- 

 fication, appeared in September, 1848, and was followed in May and July, 1849 , by a 

 paper on Some Points to be considered in Chemical Classification. In January, 1850, 

 appeared a paper on the Constitution of Leucine, with Kemarks on the late Researches 

 of Wurtz ; and hi March, 1852, one on the Compound Ammonias and the Bodies of the 

 Cacodyle Series. In March, 1854, I published a summary of the views embodied in 

 the preceding papers, commenting especially on the first one, in an essay on The 

 Theoretical Relations of Water and Hydrogen, and vindicating for myself the priority 

 in those views of chemical theory which had since my announcement of them been 

 adopted by Gerhardt, Williamson, Wurtz, and other chemists. The publication by 

 Wurtz of a criticism of Kolbe, in 1860, led me to write the following paper on the 

 Theory of Types in Chemistry, in which I have concisely traced the history of the de- 

 velopment of my views. It appeared in the Canadian Journal for March, 1861, and in 

 the American Journal of Science for the same month of the same year. I have, in re- 

 printing it, added an appendix on Nitrogen and Nitrification. 



IN the Annalen der Chemie und Pharmacie for March, 1860 

 (CXIII. 293), Mr. Kolbe has published a paper on the natural 

 relations between mineral and organic compounds, considered 

 as a scientific basis for a new classification of the latter. He 

 objects to the four types admitted by Gerhardt, namely, hydro- 

 gen, hydrochloric acid, water, and ammonia, that they sustain 

 to organic compounds only artificial and external relations, while 

 he conceives that between these and certain other bodies there 

 are natural relations, having reference to the origin of the 

 organic species. Starting from the fact that all the bodies of 

 the carbon series found in the vegetable kingdom are derived 

 from carbonic acid, with the concurrence of water, he proceeds 

 to show how all the compounds of carbon, hydrogen, and 

 oxygen may be derived from the type of an oxide of carbon, 

 which is either C 2 4 , C 2 2 , or the hypothetical C 2 0. 



