October 31, 1919] 



SCIENCE 



421 



antagonizing salt must be of such a nature 

 that its contact (as metal) with passive iron 

 promotes passivity rather than activity; thus 

 it is well known that contact of passive iron 

 with copper, lead and other baser metals 

 causes activation, while contact with mercury 

 and the nobler metals has no such effect and 

 indeed promotes passivity. Hence any metal- 

 lic particles of the former class which may 

 be deposited on the iron surface serve as 

 activating centers (i. e., are anodic relatively 

 to passive iron), while those of the latter class 

 have a reverse or passivating influence. The 

 ability of any cation to prevent activation 

 thus depends upon the electrical potential of 

 the metal in relation to that of the passive 

 iron surface. In other words, the passivating 

 effect is a direct function of the oxidizing 

 potential of the ion in question, i. e., the 

 readiness with which it parts with its positive 

 charge (or receives electrons). 



As already shown, the activating effect of 

 the ISTaNOj solution is equally well prevented 

 by the addition of small quantities of salts 

 with strongly oxidizing anions, like K„Cr,Oj 

 or KMn0.j; oxidizing non-electrolytes like 

 H,0„ and OsO^ have a similar influence. 

 Ionic antagonism is thus not a function of 

 the sign of the ionic charge, but of the special 

 chemical — more specifically oxidizing — proper- 

 ties of the ion. Non-electrolytes with similar 

 chemical properties are equally effective. All 

 of these phenomena have parallels in the 

 behavior of living systems. 



Pure solutions of AgNOg, HgCNO.,),, 

 K^Cr^O^ and KMnO^ both preserve passivity 

 and have a rapid passivating action on active 

 iron. An exposure of two or three seconds to 

 m/20 Ag]SrO„ or HgClSrOj)^ is sufficient to 

 confer passivity upon an active wire. The 

 velocity of the passivation-process is high; 

 in a series of experiments with solutions of 

 AgNO., (m/10, m/20, m/40, m/80, m/160) it 

 was found that even in the m/WO solution an 

 exposure of three seconds was usually suffi- 

 cient for passivation. Saturated KMnO^ 

 passivates with exposures of one second or 

 less; K„Cr.,0_ is somewhat slower in its 

 action. 



The essential results of experiments with 



surface-active organic compounds (anaesthe- 

 tics) can be summarized briefly, m/20 CuSO^ 

 was used, containing in solution the compoimd 

 under examination; the rate of activation was 

 compared with that observed in the pure 

 m/20 CuSO^. In general such compounds, 

 unless of a definitely oxidizing chemical char- 

 acter (e. g., nitro compounds or nitrate esters), 

 exhibited little or no effect in either retarding 

 or accelerating activation. The higher ali- 

 phatic alcohols, however (n-hexyl, n-heptyl, 

 n-octyl, capryl), had a moderate retarding in- 

 fluence in saturated solution, an efl^ect prob- 

 ably dependent on the viscosity of the ad- 

 sorbed layer and the lowered electrical con- 

 ductivity; little effect was found with the 

 lower members of the series. Chloroform, 

 ethyl ether, carbon tetrachloride, ethyl and 

 phenyl urethanes, fatty acid esters (ethyl ace- 

 tate, propionate and butyrate), chloretone, 

 paraldehyde, chloral hydrate, benzol, naphtha- 

 lene, phenanthrene, all showed little or no 

 retarding action. On the other hand, ethyl 

 nitrate had a well marked antagonistic effect, 

 in one case prolonging passivity for more than 

 twenty-four hours; nitromethane and aeetoni- 

 trile also caused distinct retardation. Par- 

 allels with the general pharmacological action 

 of the above compounds are thus not apparent 

 in these experiments, but the existence of such 

 parallels is perhaps hardly to be expected. 

 In the living cell the characteristic action of 

 these compounds appears to depend largely 

 upon solution in the organic solvents of the 

 protoplasm, especially the lipoids ; the stability 

 of the protoplasmic film is correspondingly 

 altered, being increased at the ansssthetizing 

 concentrations of the compounds. In the 

 metal no such process of solution can occur, 

 and whatever influence is exerted appears to 

 depend upon the physical properties of the 

 adsorbed layer or upon the direct chemical 

 action of the compound upon the metal. 



Ealph S. Lillie 



PHILADELPHIA MEETING OF THE 

 AMERICAN CHEMICAL SOCIETY 



' The general description of the meeting held 

 September 2 to 6, 1919, has already been printed 



