180 



SCIENCE 



[N. S. Vol. XLIX. No. 1260 



positive and the other negative. Also that 

 atoms may form unstable compounds of higher 

 valence when one of the new valences is posi- 

 tive and the other negative. The instability of 

 such compoimds is due to the fact that they 

 contain two atoms or gToups of opposite sign. 



This is closely related to Abegg's contra- 

 valences, according to which the non-metallic 

 elements, in particular, exhibit maximum pos- 

 itive and negative valences the sum of which 

 is eight. Thus sulfur has a negative valence 

 of two in hydrogen sulfide and a positive 

 valence of six in sulfur trioxide and in sul- 

 furic acid. But sulfur very readily assumes 

 three negative valences, in such compounds as 

 triethyl sulfoniiun iodide, (02115)38!, in which 

 it has also assumed one positive valence. We 

 may assume that methane, in a similar manner 

 forms with chlorine the compound CH^C1+C1~, 

 which at once splits off hydrochloric acid. 



It seems worth while to remark that we 

 have much need of revising our conception of 

 the non-metallic elements as being negative 

 elements. This is based on the fact that the 

 halogens when imivalent form their most 

 stable comxwunds as negative atoms and also 

 because nitrogen, suKur and similar elements 

 form very stable negative groups, such as SO4, 

 NOg, etc. "We are a little apt to forget that 

 oxygen forms the negative part of these 

 groups and that nitrogen and sulfur are 

 positive in them. Some apparent anomalies 

 in the laws for the orientation of substituting 

 groups in benzene derivatives are easily ex- 

 plained when these facts are kept in mind. 



It will have been noticed that very much 

 importance is attached, above, to additions 

 and decompositions in which the two groups 

 or atoms added or split off are of opposite 

 sign. Nef, Michael and others have often 

 emphasized the importance of reactions of 

 this type but at a time when an accurate con- 

 sideration of the positive or negative char- 

 acter of the atoms or groups involved was 

 not in vogue. 



Some of our ideas need revision, as it seems 

 to me, in this regard. Let us take the com- 

 monly accepted formula of nitrous oxide. 



II >0. 



The compound is formed by the decomposi- 

 tion of ammonium nitrate. This would al- 

 most certainly begin by the splitting off of 

 hydrogen and NO3, giving ammonia and nitric 

 acid. Besides recombining to ammonium ni- 

 trate part of the armnonia would add itself 

 to the nitric acid, giving 



/OH 



0=N— OH. 



\NH2 



Such a compound would lose water, giving 



/OH 



o=n4 



^NH 



first and then 0=N^N. Such a structure 

 takes account of the probability that one 

 nitrogen atom remains positive and the other 

 negative throughout the series while the for- 

 mula usually given implies that at least one 

 valence of one nitrogen atom changes from 

 negative to positive. The formula here pro- 

 posed also seems more in accord with the ease 

 with which nitrous oxide gives up its oxygen. 



I can not take the time to consider the very 

 interesting discussions of Falk and Nelson, 

 of Fry and of Jones nor the valuable ad- 

 ditions to our experimental knowledge made 

 by the last two. As was remarked at the be- 

 ginning, every important advance must com- 

 bine experimental evidence with new explana- 

 tions of natural phenomena. 



G. 'N. Lewis has proposed the hypothesis 

 that carbon compounds are not held together 

 by polar valences because they do not readily 

 ionize. It seems possible that this is true in 

 some cases but it is difficult to believe that 

 there is any very essential difference between 

 the reaction of methyl iodide with silver ni- 

 trate and that of potassium iodide with the 

 same reagent. 



Werner distinguishes between primary va- 

 lences which hold simple compounds together 

 and also cause the binding of carbon atoms, 

 and secondary valences, which are effective 

 in the formation of complex, molecular com- 

 I)ounds. Strong reasons have been given for 

 thinking that the ammonium compounds are 



