Brown— The Densities and Specific Heats of some Alloys of Tron. 83 
by 0:003 for every 1 per cent. of added silicon; but further additions of silicon 
have little or no effect. 
6. Chromium, Copper, and Cobalt, when separately added to iron, have very 
little effect on the specific heat when a high percentage of carbon is present. 
7. Aluminium, when added to iron up to about 3 per cent., seems to have little 
or no effect on the specific heat. 
PART III. 
In 1899 a paper on the magnetic properties of these alloys was read before 
this Society,* in which the energy dissipated per cycle was given for some of these 
steels. It will, therefore, be of interest to apply the results now obtained for the 
densities and specific heats, and to calculate the temperature rise in the iron when 
subjected to a series of cycles, as in commercial work. We will take two cases— 
(1) the teeth in the armature core of a direct current dynamo, and (2) the core 
of an alternating current transformer. The frequency of the magnetic flux in the 
armature of a direct current dynamo is seldom higher than 20 per sec., and the 
induction about 16000 c¢.g.s. lines, and in transformers the mean induction 
employed in practice is 6000 c.g.s. lines at a frequency of 50 per sec. 
In the following table are given the temperature rise in degrees centigrade 
for one hour, and the energy dissipated per cycle in the two cases, as well as the 
principal constituent in each alloy other than the iron, 
The values in the fifth column for the energy dissipated have been calculated 
from those in the third column by means of Steinmetz’s formula. 
Assuming that all the heat produced by hysteresis remains in the iron, we 
have 
1 
; |@.aB 
de 
Jpo 
when the numerator of the fraction expresses the energy dissipated per complete 
cycle, and J= Joule’s equivalent 42 x 10° ergs, p = the density of the material, 
o = the specific heat, and 6 = the temperature rise in degrees centigrade. 
* Barrett, Brown, and Hadfield. Scient. Trans. Roy. Dublin Soc., 1900, vol. vii., pp. 67-126. 
TRANS. ROY. DUB. SOG., VOL. IX., PART VI. 12 
