HlUIKiMAX. — TllKKMODYXAMIC 1'K()I*KUTIP:S OK WATER. .'^10 



Tlie procedure in using- the apparatus in tliis finally modified form 

 is as follows. The manganin coil is first screwed into the lower part 

 of the cylin(]er. The rubber washer used to make this plug tight is 

 one cut with a standard set of cutters, so that all the washers used for 

 this purpose are always the same in size. This insures that the 

 distortion due to the compression of the washers shall always be the 

 same. The steel shell with the water in it is next introduced from 

 above. The quantity of water is previously determined by weighing. 

 It is desirable not to fill the shell to closer than 1 / 4" of the top, ex- 

 perience having shown that otherwise water is likely to spill out and 

 fiml its way to the manganin coil. The kerosene is next introduced 

 into the cylinder from above. To ensure entire filling of all parts of 

 the apparatus and the exclusion of air, only part of the kerosene is at 

 first poured in, the air is then exhausted by attaching the mouth of the 

 cylinder to an air pump, or simply by exhausting with the lungs, and 

 then the remainder of the kerosene poured in. The amount of kero- 

 sene is determined by weighing the dish from which it is poured before 

 and after filling. Because of the wetting of the dish by the kerosene 

 it is not always possible to obtain exactly the amount of kerosene 

 desired each time, but the variation is seldom over 0.02 gm., and the 

 very slight effect of this discrepancy may be corrected for, as will be 

 described later. Finally the movable plug is introduced into the 

 top of the cylinder, taking particular pains not to allow any of the 

 kerosene to escape in the process. Here again the rubber washer used 

 has been cut with standard cutters, so that the amount of rubber 

 used here is also the same in all the experiments. The cylinder is 

 then placed in the thermostat, and the zero of the manganin coil 

 read at the temperature of the room. The thermostat is then adjusted 

 for the desired temperature and the cylinder seasoned for the run by 

 the application of pressure. 



A preliminary seasoning is necessary because of the hysteresis 

 shown by the cylinder, and this hysteresis is shown with respect to 

 both pressure and temperature. Many of the early results were 

 somewhat in error because the necessity of this seasoning for tempera- 

 ture as well as for pressure was not clearly recognized. The method 

 of seasoning to be adopted depends on the kind of data which it is 

 desired to obtain from the run, whether the compressibility at con- 

 stant temperature or the thermal dilatation at constant pressure. 

 If it is desired to determine the isothermal compressibility, the season- 

 ing consists simply in raising the pressure through the entire range 

 and releasing several times. It was found by experiment that three 



