18 Conductivities and Viscosities in Pure and in Mixed Solvents. 



as in the case of the latter, but that the solvent expanded linearly with 

 rise in temperature, the variation of the specific volume being repre- 

 sented by V = 0.8674X (10.0007422). 



Rohler also found that, according to Faraday's law, copper dissolves 

 in formamid at all dilutions, half as univalent and half as bivalent ions, 

 at the anode. He obtained a good separation of copper with a weak 

 current, but with a stronger current the metal separated as a dark 

 slime. Similar results were obtained with lead, zinc, and tin. With 

 all of these metals in air, more metal dissolved at the anode than 

 separated at the cathode. The electrolysis of nickel, cobalt, iron, 

 aluminium, and magnesium salts yielded no appreciable amount of 

 metal at the cathode. Rohler also noted the formation of metallic 

 formamidates and of crystalline double compounds, which will be con- 

 sidered in discussing the properties of formamid as compared with 

 those of water. 



In a quite recent paper Walden 1 gives an account of his cryoscopic 

 work in this solvent. In his preliminary discussion he states, as his 

 reason for adopting the freezing-point rather than the conductivity 

 method for measuring dissociations, that the high specific conductivity 

 of the solvent (as measured by him) rendered it impossible to obtain 

 accurate data by the latter method. However, as will be pointed out 

 later, by our method of preparing formamid a solvent may be obtained 

 with a specific conductivity comparable with that of water, the loss of 

 material being only one-third that experienced by Walden. 



Walden determined the freezing-point constant of formamid, and 

 gives the value 35.0 as the mean of six determinations, using urea, 

 acetic ester, diethylsulphite, ethyl acetate, mesityloxide, and nitrana- 

 line, respectively, as the solute. He also studied the dissociation of a 

 number of electrolytes, including salts and both strong and weak acids, 

 and pointed out that all binary salts are strongly ionized at relatively 

 high concentrations, the ionization increasing slowly to the limit a = 100, 

 as in water; the limit, however, being reached at a smaller dilution in 

 formamid. The same was found to hold for acids, except in the case 

 of those where combination took place between solvent and solute, as 

 in the case of some of the strong acids, the values found being smaller 

 than those for water. 



FORMAMID AS A SOLVENT. 



Formamid is a clear, colorless, and somewhat viscous liquid, melting 

 at 18, and boiling under atmospheric pressure with partial decomposi- 

 tion at 200 to 212. It reacts neutral to litmus and is quite hydro- 

 scopic, undergoing a slow hydrolysis at ordinary temperatures into 

 ammonium formate. This solvent is the most closely allied to water 

 in its properties of all the organic solvents. The two are miscible in 



'Bull. Imp. Acad. Sci., St. Petersburg (1911). 



