﻿effect of Temper, in case of Steel. 



281 



(commutation) ; to submerge equal surfaces of steel electrode 

 in all cases. The results follow : 



Annealed at 20°. 

 No. 9. No. 10. 



€ x 10 z ex 10 z 



±18 ±28 



±6-023 



Annealed at 360°. 



No. 5. No. 6. 



e x 10 z ex 10 z 



+ 93±11 +85±6 



+ 0-089 



Annealed at 100°. 

 No. I. No. 2. 



exlO z ex 10 z 



+ 12 ±5 +28 ±9 



+ 0-020 



Annealed at 450°. 



No. 7. No. 8. 



e x 10 z ex 10 z 



+ 128 + 15 +82±9 



+ 0-105 



Annealed at 190°. 

 No. 3. No. 4. 



exlO z ex 10 z 



+ 33 + 7 +20±8 



+ 0-027 



Annealed at 1000°. 



No. 11. No. 12. 



e x 10 z ex 10 z 



+ 166 + 5 +205 + 3 



+ 0-185 



A few supplementary data are given in the next table, where 

 JSTos. I and II are (+) iron /steel (— ) couples, both metals softened 

 at red heat; No. Ill a couple of two nominally identical iron 

 wires ; Nos. IV and Y, couples consisting of steel in the com- 

 mercial drawn state (+), and the same steel softened at red 

 heat (— ). The couples are immersed in distilled water. The 

 extreme positive character of the commercial wires is in accord 

 with the data for carburation, p. 277. 



e x io z = 

 Mean e x 10 z = 



I. 



+ 26 + 3 



II. 

 63 + 2 



+ 45 



III. 

 ±20 

 ±20 



IV. 

 •69±5 



Y. 



■65±2 



■67 



The general results of these measurements are in accord- 

 ance; the variations of potential, when taken as a whole, regu- 

 lar and decided. They show that as hardness increases the 

 hydroelectric position of steel moves continually in an electro- 

 negative direction. The electromotive forces encountered are 

 larger for the electrolyte distilled water than for zinc sulphate. 

 The total range of variation in the former case (water) may 

 exceed 0*25 volt. For zinc sulphate it scarcely reaches the 

 one-third of this amount and decreases as the time of immersion 

 increases. After submersion, moreover, the original electro- 

 motive force is not fully restored even by rubbing the elec- 

 trodes.* When steel is immersed in water the effect of repeated 

 scouring seemed to be an increase of electromotive force. 

 These and similar anno} r ances which make the study of polari- 

 zation phenomena so unsatisfactory are too well known to need 

 further comment here. 



If we avail ourselves of the observations made above on the 

 rate of solution of tempered steel, we may infer, consistently 

 with all the facts adduced, that inasmuch as the tempered elec- 

 trode is covered with hydrogen at a greater rate than the hard 



* After long exposure of the wires to air the original force again appears. 



