72 Studies on Solution. 



EXPERIMENTAL. 



PREPARATION OF THE SOLVENTS. 



Formamid. The formamid used in this work was prepared in the 

 same manner as that used by Davis and Putnam i. e., the so-called 

 c. p. material was subjected to repeated fractionation in the vacuum 

 distilling apparatus described by them. By this method it was pos- 

 sible to obtain formamid of a specific conductivity comparable to that 

 of water with a minimum loss of material. 



The conductivity values for the solvent used in this work was some- 

 what lower than that used earlier, ranging from 0.7 to 1.5X10" 5 

 as compared with 2.7X10" 5 . The average density was 1.130 at 25, 

 the viscosity 0.0332 at the same temperature. A very small fraction, 

 representing only about one- tenth of the original volume, was obtained 

 after about three fractionations more than required for preparing the 

 solvent in large quantities which had a specific conductivity of about 

 2X10~ 6 , a viscosity of 0.03358, and a density of 1.1331. Merry and 

 Turner 1 mention having obtained a similar fraction by repeated crys- 

 tallization with a viscosity of 0.03359 and density of 1.1312. 



After formamid had been recovered from salts used in making about 

 15 "sets" 2 of solutions, it was found by continued fractionation that a 

 product could be obtained which showed a specific conductivity of 

 0.83 X 10~ 5 at 25. This value is quite comparable with those obtained 

 when formamid is purified from the commercial product. The infer- 

 ence drawn from this observation is that the salts do not alter the pur- 

 ity of the solvent. It was also observed that formamid upon standing 

 in sealed glass-stoppered Erlenmeyer flasks for a period of four months, 

 June-October 1916, in a dark closet, increased in specific conductivity 

 only about ten-fold. The values observed were 0.7 X 10~ 5 and 0.97X 

 10~ 4 at 25. 



Formamid with a specific conductivity of 0.70X 10~ 5 at 25 offers no 

 great advantage over that with an average specific conductivity of 

 about 1.5X 10~ 5 at 25, with the important exception of a lower solvent 

 correction. 



When the formamid was recovered from mixtures with ethyl alcohol 

 its specific conductivity would reach a value of the order of 1 .5 X 10~ 5 at 

 25 in about the same number of fractionations as when recovered from 

 pure formamid solutions, but on standing the specific conductivity 

 soon increased and in the course of 3 or 4 days became too large for 

 conductivity measurements. This suggests a possible reaction between 

 formamid and alcohol, the products of which are more difficult to 

 remove by fractionation than the traces of ammonium formate result- 

 ing from hydrolysis of pure formamid by moisture from the air. Fur- 



Journ. Chem. Soc., 106, 748 (1914). 



2 By "set" is meant all the solvent required for the solutions of various dilutions. 



