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cals were separated from valerianic and acetic acid, failed to convince 

 a large number of contemporary chemists, who had contended for 

 some years against the existence of such radicals. Early in 1848, 

 Dr. Frankland commenced his attempts to isolate these bodies by 

 direct and unexceptionable reactions. Taking the isolation of the 

 elementary radical, hydrogen, by the action of zinc upon hydriodic 

 acid, as his type, he succeeded, in the laboratory of Professor Bunsen 

 at Marburg, in isolating from their iodides the compound radicals 

 methyl, ethyl, and amyl ; thus establishing the complete homology 

 of these substances with hydrogen. 



The subsequent prosecution of these researches also led Dr. 

 Frankland to the discovery of a new series of remarkable organic 

 compounds, containing the metals zinc, tin, and mercury, united 

 with the radicals before mentioned. These metals had not been 

 previously known to enter into combinations of that class. The 

 compounds of zinc with methyl and ethyl have, moreover, proved 

 most valuable bodies in the hands of Frankland, Hofmann, and 

 others, for effecting substitutions which had previously been im- 

 practicable. 



The laborious and masterly researches of Bunsen on cacodyl 

 had rendered this most remarkable substance an object of the 

 highest interest to chemists ; nevertheless, its isolated position, and 

 the complicated reactions attending its formation, stood in the way 

 of any satisfactory conclusion as to its rational constitution. The 

 study of the organo-metallic bodies containing zinc, tin, and mercury, 

 and of those discovered by Lowig and others, led Dr. Frankland to 

 a generalization, which grouped cacodyl and the rest of those organo- 

 metallic compounds into a harmonious family, and according to 

 which these substances are formed upon the types of the inorganic 

 compounds of the respective metals with oxygen, sulphur, and other 

 similar bodies. 



In the hands of Dr. Frankland, this theory has already borne 

 fruit. Guided by it, he has succeeded in replacing the oxygen 

 of binoxide of nitrogen, by ethyl and methyl, thus obtaining two 

 members of a new series of acids ; while the formation, by one of his 

 pupils, of two new organic derivations from sulphurous acid, is 

 another result of the same important generalization. 



