Electrical Conductances of Pure and Mixed Salt Solutions in the Temperature Range 0 to 25°

Abstract

The specific conductances of certain solutions of pure and mixed salts in the concentrations occurring in sea water have been measured. The compositions of the solutions, the methods of preparation, and the values of specific gravity used in calculating the equivalent conductances have been discussed by the authors.2 The measurements were made a t 0, 5, 10, 15, 20, and 2 5 O , using the apparatus and employing the technique previously described. aObserved deviations in measurements did not exceed 0.02%. Duplicate solutions were prepared and run in almost all instances. No discrepancies were found between duplicate samples since the experimental data and the calculations were checked repeatedly. The principal sources of error were in filling the cells rather than in preparing the solutions or in measuring the resistances. Uncertainties due to small temperature fluctuations were reduced to low values by taking several independent readings of the resistance of each cell a t each temperature. Duplicate determinations usually were made in different cells at different times. This served as a check on the cell constants as well as a means of reducing experimental errors. ResultsData.-The specific conductance and equivalent conductance data are listed in Tables I to V. Values of temperature coefficients of equivalent conductance are also included.The conductances of sodium chloride solutions and of potassium chloride solutions a t 25' have been determined by Shedlovsky4 whose measurements were based on the standard recommended by Jones and B r a d~h a w .~ The results of Shedlovsky, data from the "International Critical Tables" converted to the same basis, and the results of the present work on these solutions are (1) Paper read at the Ninety-sixth Meeting of the American (2) Bremner, Thompson and Utterback, THIS JOURNAL, 60, 2616-(3) Bremner and Thompson, ibid., 59, 2372-2374 (1937). (4) shown in Fig. 1. The agreement between the results of Shedlovsky and those reported here indicates the reproducibility and consistency which can be obtained with the apparatus and technique now available. Temperature Coefficients.-Average values of the temperature coefficients were computed for each 5' interval by means of the equation where A, is the equivalent conductance at a given temperature. These results were plotted against temperature, and the values of the coefficients a tTABLE I ELECTRICAL CONDUCTANCES AND TEMPERATURE COEFFI-CIENTS OF EQUIVALENT CONDUCTANCE FOR SODIUM CHLORIDE SOLUTIONS Mg. eq. per Specific Kg. water Liter s o h cond. (108) 466.377 341.198 193.318 96.116 466.377 341.198 193.318 96.116 466.377 341.198 193.318 96.116 466.377 341.198 193.318 96.116 466.377 341.198 193.318 96.116 466.377 341.198 193.318 96.116 25' 461.184 43537 338.168 32902 192.109 19595 95.678 10247 461.810 39291 338.611 29678 20 O 192.348 17659 95.793 9225. g 15' 462.335 35187 338.976 26558 192.540 15787 95.884 8238.9 10' 462.750 3 1230 192.682 139% 339.256 23549 95.948 7286.7 5 O 463.042 27423 339.439 20659 192.763 12246 95.981 6373.1 0' 463...

Electrochemical analysis section :

“…Our experience has confirmed the observation that a major source of random error is in the filling of cells [53]. We have obtained standard deviations less than 50 …”

“…Figure 15. Percentage deviations from test equation 44 Equation (46) has not been mentioned in the foregoing discussion because it was not tested on a strictly comparable basis. The measurements were made with a parallel R-C bridge arm and had to be recalculated to the equivalent series values by Equations (52) and (53) in order to apply Equation (46). …”

“…Capacitances were measured with much less accuracy than resistances and the application of Equations (52) and (53) introduced an undetermined error. Although Equation (46) is a fit of R vs o oo j points were omitted when the corresponding value of the series capacitance appeared clearly discordant Equation (46) reproduces the data points more closely than Equation (44) Figure 16 It is apparent from Figure 15 that Equation (48) behaves very poorly at the lower frequencies, probably due to the neglect of higher terms in the polynomial expansion of Equation Percentage deviations from test equation 39 Inclusion of the term in oo improves the fit appreciably reducing the standard deviation from 0.047 to 0.015 ohm.…”

Electrolytic conductivity of mixed electrolyte solutions

“…Thus, it is of interest to examine the conditions for a linear behaviour according to Eq. (16), and to test the validity of Eq. (17) by performing measurements with 1 : 1 electrolytes having widely differing A '-values.…”

The Statistical Description of Precision Conductivity Data for Aqueous Sodium Chloride

“…There was a notable shortage of data collected at 0°C, only 11 observations being found ( Fig. 1) [14,21,31]. Gaps in the data existed at other temperatures; at 50°C there was no data below 0.01 mol·L −1 , at 40°C there was no data below 1 mol·L −1 , and at 45°C there was no data between 0.01 and 1 mol·L −1 .…”