158 Conductivity of Aqueous Solutions. Part VI. 



of residue; and a combustion of 0.86 grams of solution (containing 0.50 

 gram or 14.3 millimols NH 4 OH) gave 2.2 mg. BaCO s * corresponding 

 to 0.5 mg. or 0.011 millimol C0 2 . Special precautions were taken to 

 exclude carbon dioxide in diluting the solution. Neither the original sam- 

 ple nor the stock solution prepared from it gave the slightest turbidity 

 with barium hydroxide even on standing. The absence of any consider- 

 able impurity is also confirmed by the agreement (within 0.01 per cent) of 

 the conductance of the stock solutions with that of one prepared by 

 R. B. Sosman in this laboratory from liquid ammonia distilled from 

 sodium. The three separate solutions prepared by us at different times also 

 agreed in conductance within 0.1 per cent. These stock solutions were 

 standardized by titration, using methyl orange as an indicator, against a 

 new hydrochloric acid solution which by precipitation with silver nitrate 

 was found to contain 115.38 milli-equivalents per kilogram solution. f The 

 more dilute solutions (30 and 10 milli-normal) were prepared from 

 weighed portions of the stock solutions by adding weighed quantities of 

 water of specific conductance 0.5 X 10~ 6 entirely out of contact with air 

 containing carbon-dioxide. No correction was applied to reduce the con- 

 tent-by-weight to volume concentration at 4, since this amounted to less 

 than 0.1 per cent even with the 100 milli-normal solution. The concentra- 

 tions of the three stock solutions in milli-equivalents per liter at 4 were 

 as follows: No. 1, 97.07; No. 2, 99.90; No. 3, 102.594 



The ammonium chloride used was made by neutralizing some of the 

 "strictly chemically pure" ammonia water above referred to with freshly 

 distilled "chemically pure" hydrochloric acid, and crystallizing the salt three 

 times from hot water by cooling. The salt was dried by heating in an open 



*The products of combustion were passed through barium hydroxide solution and 



the precipitate filtered off out of contact with the atmosphere and weighed. 



fDerived from the following data : 



Solution taken (grams). 103. 55 104.31 148.07 103.17 104.6 

 AgCl obtained (grams). 1.7139 1.7272 2.451 1.7094 1.722 

 Millimols per kilogram.115.44 115.48 115.46 115.56 115.5 



The mean of these values is 115.49, which reduced to vacuo becomes 115.38. The 

 equivalent conductance at 18 was found to be 349.9 while the value of Goodwin 

 and Haskell interpolated for this concentration is 350.2. 



^Derived from the following data : 



Stock Solution No. 1 : 



Solution taken (grams). 182.78 178.86 119.07 

 HC1 solution used do.. 153.79 150.51 100.16 

 Milli-equiv. per kilogram. 97.07 97.08 97.06 



The mean of these values is 97.07. 



Stock Solution No. 2: 



Solution taken (grams). 162.25 133.78 116.65 



HC1 solution used do.. 140.51 115.84 100.95 



Milli-equiv. per kilogram. 99.92 99.91 99.87 



The mean of these values is 99.90. 



Stock Solution No. 3: 



Solution taken (grams). 161.77 179.50 116.47 



HC1 solution used do. . 143.84 159.63 103.53 



Milli-equiv. per kilogram. 102.59 102.61 102.58 



The mean of these values is 102.59. 



