Solubility System: Pentachlorophenol with Ammonium Chloride and Water
Components:

(1) Pentachlorophenol, C6HCl5O; [87-86-5] NIST WebBook
(2) Ammonium chloride, NH4Cl; [12125-02-9] NIST WebBook
(3) Water, H2O; [7732-18-5] NIST WebBook

Original Measurements

Toyota, H.; Kuwahara, M.; Nippon Dojohiryogaku Zasshi 1967, 38(2,3), 93-97.

Variables:

Ambient temperature: 27 °C
Acidity: 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0
Amount concentration (2): [NH4Cl] = 0.0 - 1.0 mol/dm3

Prepared by:

H. Ohtaki

Method/Apparatus/Procedure:

Pentachlorophenol and various amounts of NaOH and NH4Cl were dissolved in water at 27°C and the solutions were left for 3 days with occasional stirring (once a day for 1 hour). Then, the undissolved pentachlorophenol was filtered off and the pH values of the filterates were measured with a glass electrode. To each aliquot of the solutions was added hydrochloric acid to maintain their pH less than 3. The precipitates which resulted were aged and weighed.

Source and Purity of Materials:
  1. Nothing specified.
  2. Nothing specified.
  3. Nothing specified.
Estimated Errors:

Mass concentration (m/v) (1): No estimation was given for errors in the solubility measurements. However, the reported values of S/S° (S the solubility of pentachlorophenol in KCI solutions and S° its solubility in pure water) do not fall on a single smooth curve, but rather spread. Therefore, the errors may be estimated to be larger than 2-3%.

Experimental Values:
Note: Solubilities of pentachlorophenol in water versus hydrogen ion activity, in the absence of KCl, at 27°C were measured and calculated. The stoichiometric amounts of dissolved pentachlorophenol were calculated from mass balance based upon incomplete dissociation. The dissociation constant was given as Kp=[C6Cl5O-] [H+]/[C6Cl5OH] = 3.2 × 10-5 mol/dm3. This value together with the activity of the hydrogen ion, {H +}, as determined from pH measurements was incorporated in an equation for calculating the solubility:
S = [1.796 × 10-6/{H+}0.170] [1 + 3.2 × 10-5/{H+}]

Observed and calculated values reported:
105 × mol(1)/dm3104 × mol(1)/dm3103 × mol(1)/dm3
pH5.06.07.0
Observed value:4.056.058.85
Calculated value:5.346.208.90
T (°C) pH C2 (mol/dm3) Cm1 (g(1)/dm3)a x1a,c C1 (mol/dm3)b
27.0 5.0 1.0 8.390 x 10-3 5.690 x 10-7 3.15 x 10-5
27.0 5.0 5.0 x 10-1 1.377 x 10-2 9.335 x 10-7 5.17 x 10-5
27.0 5.0 5 x 10-2 3.1361 x 10-2 2.2472 x 10-6 1.245 x 10-4
27.0 5.0 0.0 3.0657 x 10-2 2.0774 x 10-6 1.151 x 10-4

(a) Calculated by F. W. Getzen. (b) Reported. (c) Calculated mole fraction based upon complete dissociation of NH4Cl. (d) pH value of solution equilibriated with precipitate.

T (°C) pH x1 C1 (mol/dm3) C2 (mol/dm3)
27.0 5.5 4.170 x 10-6 2.31 x 10-4 5 x 10-2

T (°C) pH x1 C1 (mol/dm3) C2 (mol/dm3)
27.0 6.0 1.010 x 10-5 5.59 x 10-4 1.0
27.0 6.0 9.120 x 10-6 5.05 x 10-4 5.0 x 10-1
27.0 6.0 2.0099 x 10-5 1.113 x 10-3 3.0 x 10-1
27.0 6.0 1.797 x 10-5 9.95 x 10-4 2.0 x 10-1
27.0 6.0 4.061 x 10-6 2.25 x 10-4 0.0

T (°C) pH x1 C1 (mol/dm3) C2 (mol/dm3)
27.0 6.5 1.595 x 10-5 8.83 x 10-4 1.0
27.0 6.5 2.7005 x 10-5 1.495 x 10-3 5.0 x 10-1
27.0 6.5 4.045 x 10-5 2.24 x 10-3 1.0 x 10-1
27.0 6.5 4.226 x 10-5 2.34 x 10-3 0.0

T (°C) pH x1 C1 (mol/dm3) C2 (mol/dm3)
27.0 7.0 1.9967 x 10-5 1.105 x 10-3 1.0
27.0 7.0 3.469 x 10-5 1.92 x 10-3 5.0 x 10-1
27.0 7.0 5.275 x 10-5 2.92 x 10-3 3.0 x 10-1
27.0 7.0 5.926 x 10-5 3.28 x 10-3 2.0 x 10-1
27.0 7.0 7.553 x 10-5 4.18 x 10-3 1.0 x 10-1
27.0 7.0 1.001 x 10-4 5.54 x 10-3 5 x 10-2
27.0 7.0 1.385 x 10-4 7.66 x 10-3 0.0

T (°C) pH x1 C1 (mol/dm3) C2 (mol/dm3)
27.0 7.5 1.137 x 10-4 6.29 x 10-3 1.0 x 10-1

T (°C) pH x1 C1 (mol/dm3) C2 (mol/dm3)
27.0 8.0 2.223 x 10-5 1.23 x 10-3 1.0
27.0 8.0 3.920 x 10-5 2.17 x 10-3 5.0 x 10-1
27.0 8.0 4.299 x 10-5 2.38 x 10-3 3.0 x 10-1
27.0 8.0 8.458 x 10-5 4.68 x 10-3 2.0 x 10-1
27.0 8.0 1.257 x 10-4 6.95 x 10-3 1.0 x 10-1
27.0 8.0 1.973 x 10-4 1.09 x 10-2 5 x 10-2
27.0 8.0 1.338 x 10-3 7.28 x 10-2 0.0

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