90 WORK OF H. R. KREIDER. 



equilibrium. This equilibrium was indicated by a constant conductivity. In all 

 cases nearly an hour was necessary. Three readings were always made and the 

 mean was taken. 



For measurements a battery jar rilled with ice and water was placed within a 

 bucket and surrounded with ice and water. The cells were placed in the battery jar 

 and covered with glass. Ample time was allowed for the temperature to reach 

 equilibrium. Frequently the first reading was repeated after an interval of fifteen 

 minutes or more, insuring equilibrium. 



Extreme precautions were necessary in washing the apparatus. No fumes were 

 permitted in the room. Immediately before using, the cells and flasks were thor- 

 oughly washed with distilled water, then rinsed several times with conductivity 

 water, and finally washed repeatedly with alcohol. This alcohol was always kept 

 pure and used only a few times before it was dried and redistilled. Ether was not em- 

 ployed in drying, since there is danger of fats being contained in it. The apparatus was 

 then carefully dried. Before a solution was made up in a flask the latter was rinsed 

 with a portion of the solvent, and the cell was rinsed with a portion of the solution. 

 In many cases of very dilute solutions the flask in which the solution was to be made 

 up was first cleaned, dried and rinsed with alcohol, the conductivity of this alcohol 

 determined, and this same alcohol was employed to dilute the solution and its conduc- 

 tivity was used for the correction for the specific conductivity of the solvent. As a 

 rule there was little change in this conductivity when the above precautions were 

 observed, and yet, because of the large volume, this change was at times quite appre- 

 ciable. 



SALTS. 



The salts used were potassium iodide, ammonium bromide, potassium sulpho- 

 c yanate, lithium nitrate, sodium iodide, copper chloride, calcium nitrate, and cobalt 

 chloride. 



In all cases the necessary precautions were observed in purifying the salts, Kahl- 

 baum's best products being employed. All were recrystallized a number of times 

 finally from conductivity water and some from absolute alcohol. All were dried at 

 a temperature of 125 to 150. Those which are very deliquescent were heated for a 

 long time, some for several days in an air-bath. Those chlorides which readily form 

 oxychlorides when heated in the air were recrystallized several times, then dried in a 

 vacuum desiccator over sulphuric acid for several days, and finally heated for a long 

 time in a current of dry hydrochloric acid gas. They were then placed in a desiccator 

 over sulphuric acid and potassium hydroxide for several days. All other salts except 

 the latter class were dried to constant weight before making up each solution. 



SOLVENTS. 



The solvents used were methyl and ethyl alcohols and mixtures of these with 

 water. Considerable difficulty was experienced in purifying methyl alcohol so as to 

 obtain it with as low a specific conductivity as possible. This low conductivity was 

 important, since there was danger of introducing considerable error due to the large 

 correction for the specific conductivity of the solvent at these high dilutions. It was 

 evident from the results that some foreign substance was contained in the methyl 



