ON THE INFLUENCE OP CAKBON, ETC., ON STEEL CORROSION. 91 



aic observed at U'22 per cent, carbon and saturation point respectively, 

 whilst the values for e.m.f. reach a minimum at 045 per cent, 

 carbon. The values given at the 0'22 per cent, carbon maximum are 

 much higher than those at the saturation point. 



In the case of the hardened and tempered steels, the values of 

 E.M.F. fall directly from O'lO per cent, carbon to a minimum at 

 approximately 0"4 per cent, to 0'5 per cent, carbon, after which a 

 rapid rise to a maximum at saturation point takes place, followed by a 

 sharp fall to 0'96 per cent, carbon. 



The relations between the values given by the various types of 

 treatment are analogous to those noted in the case of the solubilities. 

 The hardened steels are consistently electronegative to the other steels. 

 The tempered steels are electronegative to the annealed, normalised, 

 and rolled steels below O'oO per cent, carbon, whilst the relative electro- 

 chemical positions are reversed in the range from 0'7 per cent, up to 

 0'95 per cent, carbon. Very little difference is produced in this direc- 

 tion by difference in the tempering temperature, as is shown by the 

 close agreement of the results given by the two tempered series. The 

 divergence between the annealed, normalised, and rolled steels becomes 

 quite distinct above 0'3 per cent, carbon when the annealed steels 

 become the most electropositive, whilst the normalised steels take up 

 the most electronegative position in this group of steels when immersed 

 in 1 per cent. H 2 S0 4 . Below 0'30 per cent. 0. the relative electro- 

 chemical positions become confused and inconclusive. There appears 

 little doubt that the results obtained in this section of the research 

 indicate substantially the relative electro-chemical positions which would 

 be taken up by the various steels on immersion under galvanic con- 

 ditions in 1 per cent. H 2 S0 4 solution or in acid mineral waters of a 

 similar type. 



It will be observed that the resistance offered by carbon steels to 

 disintegration when immersed in solutions varies considerably accord- 

 ing as to whether the solution is of the sea-water type or is acid in 

 character, and also as to whether the conditions of immersion are 

 simple or galvanic in nature. It is impossible, therefore, to specify 

 any particular composition or treatment offering the best resistance 

 to attack under all conditions, and each case must be considered 

 according to the circumstances involved. 



Dynamic Isomerism. — Report of the Committee, consisting of Professor 

 H. E. Armstrong (Chairman), Dr. T. M. Lowry (Secretary), Pro- 

 fessor Sydney Young, Dr. C. H. Desch, Dr. J. J. Dobbie, Dr. 

 M. 0. Forster, and Dr. A. Lapworth. (Draivn up by the 

 Secretary.) 



General and Specific Absorption. 



Nearly all carbon compounds absorb light to a considerable extent 

 in the far ultra-violet. If the thickness of the column of liquid be 

 diminished the limit of transmission extends, as a rule, progressively 



