SCIENCE. 



135 



ON THE CO-EFFICIENT OF EXPANSION OF 

 GAS SOLUTIONS. 



E. 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 = 286.3425 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 i° and 2° intervals of temperature and 35 min- 

 utes for a 5 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 



thermometer which in turn has been properly calibrated 

 and compared directly with the air thermometer. 

 The following solutions of ammonia gas were used : 



Number. 



Percentage 

 of NH 3 . 



Specific 

 Gravity 

 at 14° C. 





29.00 

 16.19 

 7.96 

 5.61 

 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 -I- 4° C. 



Volumes (observed values) of Aqueous Solution of NH 8 

 Gas. 



(Water)* Per Cent. 

 NHj=o.oo. 



Per Cent. NH 3 = 2.i2. 



Per Cent. NH s = 5.6i. 



Temps. 



Volumes. 



Temps. 



Volumes. 



Temps. 



Volumes. 



18° .0 



i6°.o 



i4°° 



I2°.0 



10° .0 



8°.o 



6°.o 



4°.° 



1. 001744 

 1. 001 348 

 1 .000999 

 1. 000701 

 1. 000451 

 1.000345 

 1.000114 

 1 .000030 

 1. 000000 

 1.000073 

 1.000092 



>4°-75 



9°. 72 



4°. 76 



4° .00 



2°.8o 



i°.8o.... 



— O°.20 



— 5°. 20 



1.001114 

 1. 000413 i 

 1.000033 

 1. 000000 

 0.999958 

 o-99994i 

 0.999941 

 1.000296 



ig°.8o 



14.80 



8.80 



4°. 80 



4° .00 



i°.i6.... 



— I°.20 



- 4°-2 



- 5°.* 



— IO°.2 

 



1. 003180 

 1.001953 



1.000726 

 1.' 00106 

 1.000000 

 0.099594 

 0.999398 

 0.999298 

 0.999272 

 0.999289 







o°.o 















* The water volumes are taken from Rosetti's table. — Wiilluer Phyrik 

 Bd. III. 



Per Cent. NH3-7.96. 



Per Cent. 

 NH 3 = i6.i9. 



Per Cent. 

 NH 3 = 29.oo. 



Temps. 



Volumes. 



Temps. 



Volumes. 



Temps. 



Volumes. 



i5°.oo 



9°. 80 



4°.8o .... 

 4°. 00 



— 0°.20 



— 5°. 20 



— 10°. 20 



— 11°. 20 



— 12°. 20 



— 1 3 °.20 



1.002662 

 1.001191 

 1.000141 

 1. 000000 

 0.999417 

 0.998932 

 0.998740 

 0.998733 

 0.998760 

 0.998794 



2I°.8c 



t6°.8o 



11°. 80 



6°.8o.... 



4°.oo 



i°.8o 



- 3°.20..„ 



- 8°. 20 



— 13°. 20 



— 17°. 20 



1. 007129 

 1.004930 

 1.002874 

 1.001013 

 1. 000000 

 0.9991 10 

 0.997514 

 0.996095 

 0.994890 

 o.994i39 



i5°.oo 



i 3 °.oi.... 



n°.o6 



9°.i5-- 



7°. 28 



5°-33 



4°. 00 



3°.27— - 

 i°.i6.... 



- o°.8o 



- 2°. S I.... 



- 4°. 3 8 — - 



- 6°. 4 o.... 



1.007214 



1 -005835 

 1.004547 

 1.003303 

 1.002064 

 1.000862 



I.OOOIOO 



0.999618 



0.998350 

 0.9971*9 



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. ! Freezing. Saturation Pt. 



0.00 4°. 00 o°.oo ico°.oo 



I2.12 o°.8o — 5°. 40^?) 93°. 2 



,5.61 - 7°.20 -io°.6 83°. 1 



'7.96 —10°. 50 — 14°. 1 76°. 4 



16.19 59°- c 



29.00 39°-8 



