Conductivities and Viscosities in Formamid. 37 



That the percentage temperature coefficients of conductivity 

 increase as the viscosity of the solution increases is a relation that has 

 been brought out by all the investigations in this laboratory. These 

 coefficients for solutions in formamid have the order of magnitude 

 that would be expected from the relation of their viscosities to the 

 viscosities of the same solutions in other solvents. For example, 

 compare the coefficients for solutions of potassium iodide in water, table 

 28, with those for the same salt in formamid (table 12). 



All salts containing water of crystallization were carefully dehydrated 

 at suitable temperatures just before the solutions were prepared. 

 No thermal measurements were made of the heat of solution, but in 

 the case of sodium iodide, which crystallizes with two molecules of 

 water, a marked rise in temperature was noted when the salt dis- 

 solved in formamid, which indicated the formation of a solvate. It is 

 well known that solvated salts give higher temperature percentage 

 coefficients of conductivity than non-solvated, because complexes are 

 usually simplified by rise in temperature. In the present investigation, 

 salts crystallizing with water have given the larger coefficients, indi- 

 cating the formation of solvates analogous to the formation of solvates 

 by the same salts in water and other solvents. To illustrate this 

 relation, let us compare these coefficients for sodium chromate crystal- 

 lizing with 10 molecules of water (table 10) and cobalt bromide crystal- 

 lizing with 2 molecules of water (table 27). Also, compare sodium 

 iodide, crystallizing with 2 molecules of water (table 9) with potassium 

 iodide (table 12). The coefficients for the dilute solutions of sodium 

 chromate are probably not reliable for this comparison, as will be 

 explained under the discussion of this salt. 



SODIUM CHROMATE. 



Table 10 gives the results for sodium chromate. They are of the 

 usual order of magnitude, except for the N/1600 solution. At each 

 temperature the increase in conductivity between the N/800 and 

 N/1600 solutions is 59 per cent, which is probably due to chemical 

 action or decomposition instead of to an increase in ionization. Formic 

 acid is a strong reducing agent. Formamid may be considered as 

 formic acid in which a hydroxyl has been replaced by an amino group. 

 Both the hydroxyl and amino group are basic; therefore, we might 

 expect from this relationship that formamid would be a reducing 

 agent. The reducing action of formamid will also be discussed with 

 the results for mercuric chloride. Sodium chromate is a strong oxi- 

 dizing agent; hence, it is not surprising that there should be chemical 

 action between these two compounds when the chromate is in a highly 

 ionized condition, as in a dilute solution. The percentage dissociations 

 have not been calculated, because the conditions just referred to intro- 

 duce an uncertainty regarding them. 



