ip8 Conductivity of Aqueous Solutions. Part VII. 



solution. All of the dilute solutions were diluted in a weighed 500 c.cm. 

 flask, provided with a stopcock and delivery tube, and were forced in or 

 out by purified air. All flasks and bottles used for making or keeping 

 solutions were steamed out for several days, after standing for some time 

 filled with a dilute alkali solution. 



The water was made by redistilling ordinary distilled water, after add- 

 ing to it alkaline permanganate which had been previously boiled. It was 

 distilled from a steam- jacketed copper still, and condensed hot in a tin 

 condenser, a large part being allowed to pass away as steam. It was 

 collected only in two- or four-liter hard glass " Non-Sol" bottles furnished 

 by Whitall, Tatum & Co., and allowed to cool in these, as hot water dis- 

 solves ordinary glass appreciably. The first and last portions of the dis- 

 tillate were rejected. No water of specific conductance greater than 

 0.9 X 10" 6 at 18 was used in making up the solutions. 



The salts used for determining the conductance-capacity were sodium 

 and potassium chlorides and potassium nitrate. The sodium chloride was 

 made by precipitating Baker and Adamson "C. P." salt twice with hydro- 

 chloric acid gas. The potassium chloride was made by precipitating the 

 "C. P." salt furnished by Baker and Adamson with hydrochloric acid 

 gas, and crystallizing from hot water. The potassium nitrate was made by 

 twice recrystallizing "C. P." salt from the same source. The salt gave 

 no test for sulphate or chloride. 



In preparing the solutions, the sodium and potassium chlorides were 

 ignited in a platinum dish, the potassium nitrate dried at 130 to constant 

 weight; the proper quantity of salt was weighed out and dissolved in 

 a 2-liter flask, and the solution then diluted to the mark. The conductance 

 of a sample of the water used was tested at the same time. A fresh solu- 

 tion was made for every determination. 



Ten liters of an approximately 0.1 normal solution of hydrochloric acid 

 were prepared from strong "chemically pure" acid, as a titration stand- 

 ard.* This was analyzed by precipitation with silver nitrate, and by 

 titration against a solution of sodium carbonate, prepared from pure 

 sodium bicarbonate, using methyl orange as indicator. The acidity deter- 

 mination was practically identical with the chlorine determination. The 

 value used was 90.46 milli-equivalents per kilogram of solution.f 



*50 c.cm. of the strong acid were evaporated to dryness on a steam-bath ; the resi- 

 due was organic, and amounted to only 0.01 per cent of the total hydrochloric acid. 

 30 c.cm., evaporated with barium chloride, gave no test for sulphate. The water 

 used in diluting it had at 18 a conductance less than 1.4 X 10~ 6 . 



fDerived from the following data : 



Grams of solution 93.84 104.70 105.98 126.59 



Grams AgCl 1.2169 1.3579 1.3748 1.6425 



Milli-equivalents HC1 per kilogram... 90.44 90.45 90.47 90.49 



Mean 90.46. Average deviation = 0.02 per cent. By titration of Na 2 CO s . .90.43. 



