68 Brown—The Densities and Specific Heats of some Alloys of Iron. 
If a curve be plotted having the percentage amount of chromium as abscisse, 
and the specific volumes corrected for carbon as ordinates, it will be found that 
up to about 3°25 per cent. of chromium added to the iron the specific volume of 
the material is increased, whilst the further addition of 6:25 per cent. of chromium 
has no effect. The specific volume of the second specimen when corrected for 
carbon is 0:00112¢.c. greater than that of pure iron, and therefore the change in 
the specific volume of the material obtained by adding one per cent. of chromium 
to iron is at the rate of 0:00034 c.c.; so that up to about 3°3 per cent. of added 
chromium the specific volume of the material may be expressed as specific 
volume = 071269 + 0:00034 Cr, where Cr represents the percentage amount of 
chromium in the alloy; whilst the addition of higher percentages of chromium 
(up to at least 9°5 per cent.) has no effect on the specific volume of the alloy. 
If on adding one per cent. of chromium to 99 per cent. of iron no change took 
place in the specific volumes of the constituents, then the specific volume of the 
alloy would be 0:00027 c.c. greater than that of pure iron; and since the observed 
change is 0:00034 ¢.¢., a very slight expansion has taken place. 
Taste VII. 
CopPER STEELS. 
| Percentage Composition Specific Volume 
| Mark C | Mn | Al | Cu Density Observed Calculated Difference 
| | | 
1264 A 0-68 0°36 1°59 7°83854 | 0°12763 0:12878 — 0:00115 
1264 B 0:59 | 0°52 | 2°50 78366 | 0:12761 | 0:12837 [Riss 0:00076 
1263 C Gil” | oe 2°87 7°8470 | 0:12744 0°12708 | + 0:000386 
| 1149 A 0-04 0-16 1:00 3°75 77479 0°12907 0°12905 | + 0°00002 | 
The results of four copper steels which contain from 1°59 to 3°75 per cent. of 
copper are given in Table VII. ; and if we plot a curve having the percentages of 
copper present as abscissee and for ordinates the specific volumes of the specimens 
corrected for the presence of carbon, manganese, and aluminium, it will be found 
that the effect of the addition of copper to iron is to diminish slightly the specific 
volume of the alloy. By comparing the corrected specific volume of the first 
specimen with that of pure iron, the decrease in the specific volume is 0-:0005 c.c. 
for every one per cent. of added copper up to about 1:6 per cent. of copper; and 
the specific volume of the material is not appreciably changed by the further 
addition of copper up to about 4 per cent. 
