﻿278 



JBams and Strouhal — Hydro-electric 



annealed at 360° more easily than steel annealed at 200°. In 

 other words, generally, the rate at which solution takes place 

 increases as temper continually decreases. These curious re- 

 sults were substantiated by annealing one-half of short glass- 

 hard rods (ca. 5 cm in length) at red heat. On dissolving in 

 HC1, the diameter of the soft length is diminished more rapidly 

 than the diameter of the hard length. The diminution is usu- 

 ally greatest near the middle of the rod, where hard and soft 

 parts meet ; showing, probably, that local galvanic action is 

 here perceptible.* If we define the rate of solution as the mass 

 dissolved per unit of area per unit of time, then in case of two 

 submerged cylinders, for which during the time t the radii are 

 reduced from p c to p and from p to p' respectively, the rates, 

 cet. par., will be to each other as corresponding values of the 

 expression, 



p 



•JC* 



2 npdp 

 2?tp ' 



or as 



P 



P-P' 



The following little table contains some of the results ob- 

 tained with rods in the hard (h) and the soft (s) states respect- 

 ively, dissolved in acid, HC1, under identical conditions. The 

 rods are numbered A, B, 0, D. These ratios of rates are of 

 course subject to very large variations depending on the method 

 of annealing, passivity, etc. The table is a fair exhibit of 

 average values. 



Hates of solution of hard and soft steel. 

 2p=0'126 cm . 



Original diameter 







Diameter 2p= 







Rate 



= 





Mean 

 Rate. 





A 



B 



C 



D 



A ■ 



B 



C 



D 



li 

 s 



0-122 

 0-115 



0-123 

 0-116 



0-122 

 0-115 



0-122 



0-113 



10 

 2-7 



1-0 

 3-3 



1-0 

 2-8 



1-0 

 3-2 



1-0 

 3-0 



s 



0-116 

 0-103 



0-116 

 0-108 



0-116 



0-106 



0-115 



o-ioi 



1-0 

 2-3 



1-0 



1-8 



1-0 

 2-0 



1-0 

 2-0 



1-0 

 2-0 



h 



s 



0-090 

 0-052 



0-090 

 0-061 



0-089 



0-052 



0-090 

 0-058 



1-0 



2-0 



1-0 

 1-8 i 



1-0 

 2-0 



1-0 

 1-9 



1-0 

 1-9 



h 



s 



0-078 

 0038 



0077 

 0-029 



0-077 



0-028 



0-076 

 0-042 



*]"0 



1-8 



1-0 

 2-0 ! 



1-0 

 2-0 



1-0 

 1-7 



1-0 

 1-9 



From these results we inferred that hard and tempered steel 

 would probably be distinguishable hydro-electrically, and that 

 for the first phase of the phenomenon of annealing, at least, this 



* It is also probable that steel annealed at a temperature in very low redness 

 is more easily soluble than steel in any other state, hard or soft. 



