6 



HYDRATES IN AQUEOUS SOLUTION. 



Arrhenius cell was employed, but for the very concentrated solutions a 

 special cell was designed. The accompanying sketch (fig. 2) shows this 

 cell in section. 



The U-tube A A is 8 cm. in length and 2.8 cm. in diameter. The ground 

 stoppers BB are filled with paraffin, which serves to hold the tubes cc rigidly 

 in place, thus insuring a constant distance between the electrodes. Each 

 stopper is numbered corresponding to a number placed on the ends of the 

 U-tube, so that the electrodes would not be interchanged. Furthermore, 

 by means of fine vertical lines cut on each stopper and the necks of the 

 U-tube, the electrodes could be returned to exactly the same positions each 

 time. That there was no alteration in the distance between the electrodes 

 was carefully established by a series of determinations of the cell constant 

 on successive days, with the result that the differences were well within the 

 limit of experimental error. The electrodes are of thick sheet platinum, and 



are 2.5 cm. in diameter. 



All of the conductivity measurements were made 

 at 0. The bath by which the solutions were main- 

 tained at this temperature was prepared in the follow- 



ing manner: 



A glass battery-jar was filled with finely crushed, 

 pure ice, to which was added a small volume of water. 

 This jar was placed in a large water-bath, and the 

 space between was packed with well-crushed ice. By 

 this means it was found easy to maintain the solution 

 in the conductivity cell to within five-hundredths of a 

 degree of the true zero. The ice in the battery- jar was 

 stirred occasionally, and the temperature of the bath 

 was noted frequently, to insure the measurements be- 

 ing taken at 0. 



At a later stage of the work it seemed very desira- 

 ble to supplement the freezing-point and conductivity 

 measurements with determinations of the boiling-point elevations and the 

 refractive indices of some of the solutions. For the former determinations 

 the boiling-point apparatus devised by Jones* was employed, while for the 

 refractivity measurements use was made of the well-known Pulfrich refrac- 

 tometer. 



With the exception of the pipettes, the volumetric apparatus used was 

 specially made and carefully calibrated for this investigation. The volu- 

 metric apparatus consisted of a series of measuring flasks, a burette, and a 

 series of pipettes. The pipettes were never used in making the dilutions. 



*Amer. Chem. Journ., 19, 581 (1897). 



FIG. 2. 



