Brown—The Densities and Specific Heats of some Alloys of Iron. 73 
JPANIRIS IOC. 
Sprciric Hear. 
In the determination of the specific heats of the specimens, the method of 
mixtures was employed, and a form of Regnault’s calorimeter used, in which the 
body to be tested is suspended in an air chamber and heated by means of a 
steam jacket. The apparatus was placed well away from the boiler and screened 
from currents of air, and the exhaust from the steam jacket took place into the 
outer air by means of a pipe let through the sash of a window. This method 
of getting clear of the exhaust steam allowed the room to be kept at a practically 
constant temperature for two or three hours at a time. 
The calorimeter when in use contained about 20 grammes of distilled water, 
-and very careful experiments were made to find its water equivalent, as well as 
that of the thermometer and stirrer, so that 2°2 gramme-degrees were taken 
throughout the investigation as the water equivalent of the apparatus. 
The loss by radiation was so small that no allowance was made for it, 
especially as the whole operation of dropping the hot body into the cold water, 
and the time occupied by the mixture in attaining a steady temperature, was 
not more than one minute. 
The thermometer was graduated in tenths of a degree Cent. from 5° to 25° C., 
and the length of one degree on stem was 13 mm., and therefore ~5° C. was 
1:3 mm., which distance could be divided by the eye, aided by a lens, into ten 
equal parts, so that 0:01° C. could be easily read. This thermometer was 
compared with a Kew standard, and found correct. An error of 0:01° C. in 
reading the temperature of the mixture would only affect the fourth decimal 
place in the value of the specific heat, and therefore the first three decimal 
places are taken as correct in the following tables. 
The specific heats of the alloys were all determined at temperatures from 
10°-18° C. and the results here given are each the mean of three or more separate 
experiments. The percentage chemical composition is repeated in the following 
tables, and the specific heat of each specimen is given, along with the thermal 
capacity per unit bulk. 
[TasLe XI. 
