64 Brown—The Densities and Specific Heats of some Alloys of Iron. 
slightly decreased and then slightly mereased up to about 4 per cent. of nickel 
present, whilst the specific volume of the material is decreased very little by the 
further addition of about 16 per cent. of nickel. 
From the curve we see that the specific volume of the material—corrected for 
carbon and silicon—which contains 20 per cent. of nickel, is 0:12630 c.c., and the 
specific volume of the constituents of the alloy, if no change had taken place, would 
be 0:1240 c.c., so that for this specimen we have an expansion of about 0:0023 c.e. 
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Percentage of Nickel. 
Fig, 1.—Nickren STEets. 
By drawing a mean line as in fig. 1, we find that the addition of 20 per cent. 
of nickel to iron decreases the specific volume of the material by 0:0006 c.c., or at 
the rate of about 0:00003 c.c. for every 1 per cent. of added nickel, so that up to 
about 20 per cent. of nickel the change in the specific volume of the material may 
be expressed as spec. vol. = 0.1269 - 0:00003 Ni where Ni represents the percentage 
of nickel present. 
For the high nickel steels, if we take a mean line through the points in fig. 1 
for the last three specimens, we find that the addition of 10 per cent. of nickel to 
an iron-nickel alloy which already contains 20 per cent. of nickel decreases the 
specific volume of the material by 0:0023 ¢.c., or at the rate of about 0:00023 c.c. 
for every 1 per cent. of nickel further added. 
