62 Brown—The Densities and Specific Heats of some Alloys of Iron. 
in the specific volumes of the constituents, then the specific volume of the alloy 
would exceed that of pure iron by 0:00308 ¢.c.; and since the observed value 
is 0:0018c¢.c., the difference, 0°00128 c.c., shows that a decided contraction has 
taken place. Taking the first three specimens in Table I., and plotting as 
abscisse the percentage amount of carbon present, and as ordinates the specific 
volumes of the material when corrected for silicon, it will be found that the 
points lie practically on a straight line which cuts the axis of ordinates at 
0:1269, the value for pure iron; hence the effect on the specific volume of the 
material obtained by adding up to about 0:2 per cent. of carbon to iron may 
be expressed thus :—specific volume = 0°1269 + 0:0018 C, when C represents the 
percentage amount of carbon added. 
By comparing the high carbon steels 1392 A and 1392 G, and also 611 with 614, 
we find that the specific volume of the material is increased by 0:0015 c.c. for 
every 1 per cent. of added carbon. 
Tasle II, 
MANGANESE STEELS. 
Percentage Composition Specific Volume. — 
Mark C Mn Density Observed | Calculated | Difference 
48 0-20 0:50 7:8456 0:12746 0:12756 0:00010 
4147 0-24 1:00 7-8354 0-12762 012772 0-00010 
53 0-41 2:25 7:7983 0:12823 0°12835 000012 
39 0:36 4:00 78352 0°127638 0°12834 0:00071 
1323 C 0-15 5-40 78411 0:°12753 0-12781 0:00028 
945 A 1:20 7:00 7:9028 012654 0-13118 0:00464 
1338 B 0-26 13:00 7-9970 0°12505 012879 0:00374 
598 1:54 18-50 79075 012646 013319 0:00673 
In Table II. the results are given for eight manganese steels which have from 
0:5 to 18-5 per cent. of manganese present; and from the specific volume columns 
it will be seen that in every case contraction takes place. 
If the values of the observed specific volumes be corrected for carbon, and the 
results plotted ina curve with the percentage of manganese as abscissee, and the 
