60 Brown—The Densities and Specific Heats of some Alloys of Tron. 
it to stand vertically on the scale-pan of a chemical balance. ‘The measurements 
were all made between the temperatures of 12° and 16° C. 
In order to find the density of the water used in each experiment, a curve was 
plotted on a large scale indicating the temperature and density of water from 
the values given in the Physical Tables of Landolt and Bornstem. There was 
also plotted on a large scale a curve showing the temperature and weight of the 
specific-gravity bottle filled with distilled water; and in the work all the usual 
and necessary precautions were taken to avoid errors. The densities of all the 
specimens were determined by means of the specific-gravity bottle; but on 
account of the small mass of the material (3 to 4 grammes) and the difficulty 
of getting them quite clear of minute air-bubbles, all the measurements were 
repeated by the ordinary hydrostatic method. In both these sets of experi- 
ments on the density, as well as the experiments on the specific heat, a Sartorius 
chemical balance was employed, which weighed accurately to one-tenth of a 
milligrame. In order to avoid any correction for the suspending thread in the 
density experiments by the second method, a very fine, strong fibre of floss silk 
was used, which weighed only about one quarter of a milligramme per metre, 
and could therefore be neglected. 
The values of the densities given below are each the mean of three or 
more different experiments, and no result was accepted that differed by more 
than one in the third decimal place. 
In the following tables are tabulated:—(1) the percentage chemical 
composition of the alloys, with the exception of the iron present, which is 
understood in all cases to make up the total to 100; (2) the observed density 
of each specimen; (3) the reciprocal of the density or the specific volume; (4) the 
mean specific volume of the alloy or that calculated from the specific volumes of 
the constituents, assuming that neither expansion nor contraction takes place ; 
(5) the differences between the calculated and the observed specific volumes of each 
sample. From the specific volume or the volume in cubic centimetres occupied by 
one gramme of the material, the effect of adding a foreign substance to the 
iron can best be seen. 
