SCIENCE. 
135 
ON THE CO-EFFICIENT OF EXPANSION 
GAS SOLUTIONS. 
OF 
thermometer which in turn has been properly calibrated 
and compared directly with the air thermometer. 
The following solutions of ammonia gas were used: 
F.. L. Nichols and A. W. Wheeler. 
The dilatometers used in this research differ essentially 
from those generally employed in the measurement of the 
expansion of liquids. Their form is shown in the accom- 
panying figure. The bulb (B) contained about 286 grms. of 
the liquid — [ at I5°C = 2S6.3425 grms.] 
The dilatometer having been filled was placed in the bath 
in the position denoted in the figure. The lower end (/) of 
the vertical part of the neck was then immersed in mercury 
by sliding up the adjustable mercury tube ( m ) to the proper 
point. Upon cooling the liquid, the mercury rose in the 
neck of the dilatometer and from its height at various tem- 
peratures the volume of the solution was calculated. 
This method was found to be of very great sensitiveness 
but its accuracy depends upon the careful observance of 
the following precautions. The neck must be accurately 
calibrated, the pressure must be kept nearly constant by re- 
adjusting, from time to time, the mercury-tube ( m ). Es- 
pecial study must be made of the time which will elapse 
after each change of temperature ; before the contents of the 
dilatometer will have assumed the same temperature as the 
bath. The authors found this interval of time to be 30 
minutes for 1° and 2° intervals of temperature and 35 min- 
utes for a 5 0 change. The bath itself must be constantly 
stirred. Finally the thermometers studied and not only 
their freezing points and boiling points ascertained, but a 
careful comparison must be made with some standard 
Number. 
Percentage 
ofNH,. 
Specific 
Gravity 
at 14 0 C. 
29.00 
16.I9 
7.96 
S- 6 i 
2.12 
.9009 
•9373 
.9673 
.9766 
•99«3 
Of these the volumes at various temperatures from + 20 
°C to the freezing points of the solutions or in the case of 
the stronger solutions to — 20°C were determined and the 
point of maximum density and freezing points noted. In 
the following table the volumes of each solution are com- 
pared with a unit volume of the same solution at + 4 0 C. 
TABLE. 
Volumes (observed values) of Aqueous Solution of NH 3 
Gas. 
(Water)* Per Cent. 
NH 8 =o.oo. 
Per Cent. NH s =s.i2, 
Per Cent. NH s =5 .6 i. 
Temps. 
Volumes. 
Temps. 
Volumes. 
Temps. 
Volumes. 
20° .O 
i8°.o 
i6°.o 
i4°.o 
12°. 0 
io°.o 
8°.o 
6°.o 
1.001744 
1.001348 
1.000999 
1. 000701 
1. 000451 
1.000345 
1.000114 
1.000030 
1. 000000 
1.000073 
1.000092 
x 4°*75 
9°*72 
4 0 . 76 
4 °-°° 
2 0 . 80 
i°.8o 
— o° .20 
— 5 0 . 20 
1.001114 
1.000413 
1.000033 
1. 000000 
0.999958 
0.999941 
0.999941 
1.000296 
i9°.8o 
14.80 
8.80 
4°. 80 
4 0 .00 
i°. 16 
— 1 0 . 20 
- 4 0 -* 
1.003180 
1.001953 
1.000726 
1.000106 
1.000000 
0-099594 
0.999398 
0.999298 
0.999272 
0.999289 
— IO° .2 
* The water volumes are taken from Rosetti's table. — Wtllluer Phyrik 
Bd. III. 
Per Cent. NH 3 — 7.96. 
Per Cent. 
NH 3 =i6.i9. 
Per Cent. 
NH 3 = 29.00. 
Temps. 
Volumes. 
Temps. 
Volumes. 
Temps. 
Volumes. 
i5°.oo 
1.002662 
21 0 . 80 
1.007129 
I5 0 .oo 
1.007214 
9 0 . 80 
1.001191 
i6°.8o 
1.004930 
i3°.oi 
1.005835 
4 0 . 80 
1.000141 
11°. 80 
1.002874 
ii°. 06 
1.004547 
4 0 . 00 - — 
1.000000 
6°. 80 
1.001013 
9°* I 5 
1.003303 
— o° .20 
0.999417 
4°.oo 
1. 000000 
7 0 . 28 
1 .002064 
— 5 0 . 20 
0.998932 
i°.8o._._ 
0.999110 
5°*33 
1.000862 
— IO° .20 
0.998740 
— 3°. 20 
°-9975>4 
4°-°° 
1. 000 1 00 
— ii°. 20 
0.998733 
— 8°. 20 
0.996095 
3 -27 
0.999618 
— 12°. 20 
0.998760 
— 13°.20 
O.99489O 
i°.i6 
0.998350 
— 13°.20 
0.998794 
— iy° .20 
°-994>39 
— o°.8o 
- 2°. 51 
- 4°-3»--~ 
— 6.40 
0.997109 
0.996020 
0.994838 
0-993585 
From these observed volumes the co-efficients of expan- 
sion were calculated and curves showing the volumes and 
co-efficients were plotted. The co-efficient curves are val- 
uable in the determination of the points of maximum den- 
sity, since they cut the base line at that point at a con- 
siderable angle, and serve to fix the temperature within 
o.i° C. 
The solutions of 2.12, 5.61, and 7.96 per cent, strength 
froze within the temperature interval reached by the com- 
mon salt and ice freezing mixture used : the stronger 
solutions however remained in the liquid state. The fol- 
lowing table gives the points of maximum density and the 
freezing points of the solutions : 
Percentage. Max. Density. IFreezing. Saturation Pt. 
4 0 . 00 
5- 6x 
796 
29.00 ....... 
o°.oo 
ioo°.oo 
— 5°-4°I(?) 
93 ° • 2 
— io°.6 
83°. i 
76° -4 
59 ° -o 
39 0 . 8 
