Brown— The Densities and Specific Heats of some Alloys of Iron. 69 
If on adding one per cent. of copper to 99 per cent. of iron no change were to 
take place in the specific volumes of the constituents, the specific volume of the 
resultant alloy would be about 0:00016 ¢.c. dess than that of pure iron; and since 
the observed change was 0:0005 c.c. an expansion has occurred. 
Tasie VIII. 
CoBALT STEELS. 
Percentage Composition Specific Volume 
Mark C Mn Si Co Density Observed Calculated Difference 
1209 C 0:25 *1:0 0°64 18 78117 0°12801 0°12943 0-00142 
1209 F 0°52 0:8 0°80 7:0 7°8326 0°12767 0°18013 0:00246 
The results for two cobalt steels are here given in Table VIII. ; and if we plot 
as before the percentage amount of cobalt present as abscissze and the specific 
volumes—corrected for carbon, manganese, and silicon—as ordinates, it will be 
seen that a straight line drawn through these corrected values cuts the axis of 
ordinates practically at the value for pure iron. 
We therefore find that the addition of 7 per cent. of cobalt to iron decreases 
the specific volume of the material by 0:0007¢.c., or at the rate of 0:0001 c.c. 
for every 1 per cent. of cobalt added. If no change were to take place in 
the specific volumes of the constituents when one per cent. of cobalt is added 
to 99 per cent. of iron, then the specific volume of the resultant alloy would 
be 0:00011l ¢.c. less than that of pure iron; and since the cbserved change is 
(0001 ¢.c., it seems that neither expansion nor contraction has taken place. 
TABLE IX. 
ALUMINIUM STEELS. 
Percentage Composition Specific Volume 
Mark C Si Cr Al Density Observed Calculated Difference 
8038 0°67 2°25 0°50 7°5930 0°13170 0°13681 0:00511 
1167 0 0:24 0:18 2°25 7°5182 0°13310 0:13396 0:00086 
1178 K 0°22 1:5 4°50 7°1582 0:18970 0:14048 0:00078 
In Table IX. are given the results for three aluminium steels which contain 
N2 
