712 



DR A. CRUM BROWN ON ISOMERIC COMPOUNDS. 



in which both oxygen equivalents are combined with the same carbon atom. 

 The constitutional formula of chloride of ethylidene is therefore 



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and that of aldehyde 



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These two series of substances are therefore metameric. 



12. The researches of Wislicenus (An. Ph. cxxviii. 1) and Lippmann (An. 

 Ph. cxxix. 81) prove that lactic acid and paralactic acid stand to one another in 

 a relation similar to that of chloride of ethylidene and chloride of ethylene ; that, 

 in fact, the former is a compound of ethylidene, with the water residue and the 



group i'^ |- CO j ' and the latter of ethylene with the same radicals. They have 



therefore the following constitutional formulae, and are metameric : — 



Lactic. 



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Paralactic. 

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III III 



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13. With regard to the two series of alcohols — the alcohols proper and the 

 hydrates of the olefines — we know, at least, that Friedel's alcohol is not absolutely 

 isomeric with propylic alcohol, but, as suggested by Kolbe, only metameric. If 

 we consider the relation of these alcohols to their aldehydes — propionic aldehyde, 

 and acetone, the aldehyde of Friedel's alcohol — we easily see that the formula 

 of propylic alcohol is 



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