218 
Proceedings of the Royal Society of Edinburgh. [Sess. 
Table III. — To illustrate the Method of Determining the Density of a Water, R. 
Density, A 18 , of standard sea-water =1 '02922. 
Exper. 
Microm. Readings. 
Height of 
Column = H. 
Microm. Readings. 
Height of 
Column 
(corrected) =h. 
Density 
= H /h 
x A 18 . 
Diff. 
from 
Mean. 
Water x in 
Tube S. 
Water R in 
Tube K. 
1 . 
42'80 mm. 
1000-80 mm. 
44'32 mm. 
1002-12 mm. 
1-02786 
- -00004 
9. 
39'80 u 
997-80 „ 
41-25 „ 
999-05 
93 
+ 3 
3. 
36'87 m 
994*87 m 
38-35 it 
996*15 
90 
± 0 
Mean = 
= 1-027901 
hr 
By py knometer A 18 = 
: 1-02797/ 
— 7 
In general practice, a simplified method of calculating the density from 
the data may be adopted. For, if the difference between the lengths of the 
two columns of water does not exceed 2 or 3 mm., on adding it to, or 
subtracting it from, the density value of the standard water, according as 
the water under examination has a greater or less density than the other, 
we at once obtain a very close approximation to the value of the density 
sought. In other words, when the densities of the two waters are nearly 
the same, the difference in the lengths of the columns is practically equal 
to the difference in their respective densities. We may here observe that 
a difference of 1 mm. in the micrometer reading indicates a change of '001 
in the value for the density. 
By applying this method to the data obtained for the water described 
in Table III., we obtain the results shown in Table IV. 
Table IV. — Example illustrating the Differential Method. 
Density of standard water x = 1 "02922 at 18° C. 
xper. 
Water x in 
Tube S. 
Water R in 
Tube K. 
Apparent 
Difference. 
Error for 
Tube K. 
Corrected 
Difference. 
Density Found. 
1. 
42-80 mm. 
44-32 mm. 
-1-1 "52 mm. 
+ 0*20 mm. 
+ 1*32 mm. 
1-02790 (1*02922 
- -00132) 
2. 
39-80 .. 
41-25 „ 
+ 1*45 it 
it 
+ 1‘25 ii 
7 ( n 
•00125) 
3. 
36*87 it 
38-35 
+ 1*48 „ 
ii 
+ 1-28 „ 
4 ( M 
•00128) 
1-02794 
By pyknometer- 
1-02797 
Diff.= 
•00003 
