The exact inception, however, of the theory of chemical valencies can be traced to an 1852 paper by Edward Frankland, in which he combined the older theories of free radicals and “type theory” with thoughts on chemical affinity to show that certain elements have the tendency to combine with other elements to form compounds containing 3, i.e., in the three atom groups (e.g., "NO3, NH3, NI3," etc.
Tako je upravičeno domnevati, da je Clemens nekaj časa preživel tudi v Parizu.