are capable of varying degrees of affinity or attraction for the electron pair. This property we have called electronegativity. Strictly speaking, there are no electropositive radicals. All radicals are electronegative to a greater or lesser degree; i. e., all have more or less attraction for the electron pair. (3) The stability of the bond is a function of the electronegativities of the radicals which it joins; i. e., of the tenacity with which the electron pair is held by the nuclei. (4) Bonds may be totally non-polar or may display a wide range of polarities. Polarity and stability are only indirectly and coincidentally related. Non-polar bonds display a wide range of stabilities (as, also, do polar bonds). A method of determining the relative degrees of electronegativity 01 organic radicals has been described and a table of electronegativities determined has been given. The rule governing the effect of substitutions upon the electronegativity of the methyl radical has been given. The existence of free radicals has been explained and the causes which give rise to them have been stated. A means of correlating molecular structure with heat of combustion has been advanced and tables compiled from the literature are offered for the comparison of calculated with observed values. In the next article of the projected series, the authors plan to extend the electronic theory somewhat and to discuss, from that point of view, the nature of the double bond, the Thiele hypothesis (1, 4 addition), the rules governing addition a t double bonds, and some of the reactions of unsaturated compounds. Later articles will deal with other types of organic compounds and reactions. The authors are aware that the attempt to confine the exposition of such a theory within reasonable space limitations may occasionally lead to the omission of details or amplifications necessary to complete clarity. The authors will be glad to extend the discussion of points which readers find confusing or open to objection, either by personal communication or through the Correspondence columns of the JOURNAL.
Romans Welded Iron 1800 Years Ago. Roman artisans in England only two t o three centuries after the time of Christ knew how t o weld iron and how to join or "solder" two pieces of iron together with copper, the Institute of Metals was told, a t its meeting, by Profs. J. Newton Friend and W. E. Thorneycroft of the Technical College, Birmingham. The specimen examined by them was a deep iron ferrule, like a modern napkin ring, that was unearthed during excavations of the Roman city of Uriconium located on the river Severn and destroyed about A.D. 380. Lead pipe manufactured and laid in Rome's water system 1800 years ago was pronounced t o be in perfect condition by William A. Cowan, chemist of the National Lead Company, Brooklyn, N. Y., in a communication to the Institute. Analysis showed that the same lead was used hy the Romans in England and Italy.-Sckncc Service
