Conductivities and Viscosities in Formamid. 



23 



liquid was observed ; but this thermometer was subsequently discarded 

 and the temperature controlled solely by the thermometer in the outer 

 bath, so as to obtain about 100 c.c. of distillate every 15 minutes. 



As a rule, starting with Kahlbaum's so-called c. p. formamid, from 

 three to four distillations yielded a product sufficiently pure for our 

 purpose. The decrease in the conductivity with successive distillation 

 is shown in table 6: 



TABLE 6. Specific Conductivity. 

 [Original material, 674.0 X1Q- 4 .] 



While the end-fraction in this case was sufficiently pure for use, 

 a fourth distillation yielded a product with a conductivity of about 

 3-4 X 10~ 5 . Although the exact minimum conductivity of this solvent 

 has thus far not been ascertained, w r e have obtained small lots with a 

 specific conductivity of 2.8X10" 6 to 4.7X10" 6 , or from 2 to 3 times 

 the value for the conductivity water used in this laboratory. Walden 

 used in his work a product with a conductivity of 7.5X10" 4 , but 

 obtained a small fraction of about 10 per cent of the original material, 

 with a conductivity of 4.7X10" 5 . Our solvent was from 35 to 40 

 per cent of the original volume with a maximum specific conductiv- 

 ity of 4.8X10" 5 , with a minimum of 1.37X10" 5 and an average of 

 2.7X1Q- 5 . 



SALTS. 



On account of the instability of the solvent formamid in the presence 

 of moisture, the salts used in this investigation were all dehydrated with 

 special care at the highest temperature which it was possible to use for 

 these substances. 



SOLUTIONS. 



The more concentrated solutions in formamid were made up by direct 

 weighing; the more dilute by diluting the more concentrated. This 

 operation was much facilitated by the use of two burettes holding 50 

 and 10 cm. respectively; the one being employed for the solvent, the 

 other for the one-tenth normal solution. Each burette was connected 

 with the reservoir containing the solvent or the solution, by a siphon 

 provided with a glass stopcock, access of moisture being prevented 

 by calcium chloride tubes connected with both the burettes and the 

 reservoirs. 



