136 Studies on Solution. 



Senter showed that neutral salts have practically no effect on the 

 decomposition of sodium chloroacetate by water 



Kellogg 1 studied the effect of the neutral salts, potassium chloride, 

 potassium bromide, and potassium iodide on the velocity of the hydro- 

 lysis of ethyl acetate. The reactions were carried out in sealed tubes 

 at 100, using a fixed quantity of ester and varying concentrations of 

 the salt solution. The results obtained show that the specific influence 

 of salts is greater in somewhat dilute solutions. As the concentration 

 is increased, the effect gradually becomes less until it reaches zero, and 

 then becomes negative in character; for example, a 4-normal solution of 

 potassium chloride hj^drolyzes the ester more slowly than pure water 

 itself. Kellogg found a decrease in the accelerating power from 

 chloride to bromide to iodide, which is in reverse order to their stability. 



Henderson and Kellogg 2 continued the investigation, using the 

 chlorides of sodium, lithium, calcium, strontium, and barium, and the 

 chloride and iodide of cadmium. They carried out the work under the 

 same conditions as before and also measured the conductivities and 

 viscosities of the solutions at the concentrations and temperatures 

 employed in the experiments; and from these calculated the degree 

 of ionization. They found that the salts which produce the greatest 

 effect are those which are the least ionized. The accelerating effect 

 of lithium chloride is greater than that of sodium chloride, although the 

 degree of ionization of the former is less, while the chlorides of calcium, 

 barium, and strontium have a greater effect than either sodium chloride 

 or potassium chloride, although they too are less ionized. Cadmium 

 chloride, the least ionized of all the chlorides studied, produced the 

 greatest effect, due probably to the hydrolysis of the salt. Henderson 

 and Kellogg concluded that the effect produced by a neutral salt on the 

 hydrolysis of ethyl acetate is due to a specific influence on the non- 

 ionized portion of the salt, rather than to any function of the ions. 



There have been several suggestions put forward to explain neutral 

 salt action. Arrhenius 3 proposed that the salts may affect the sub- 

 stance which is being hydrolyzed; that there may be present in the 

 solution an equilibrium between an active and an inactive form of 

 the substrate, and that this equilibrium may be altered through changes 

 of temperature or ionic concentration. Armstrong and Caldwell 

 concluded that the salts act by removing part of the water in the form 

 of definite hydrated compounds, and in this manner increase the 

 concentration of the reacting substance. Stieglitz explained salt 

 effect in general by the theory that the presence of salts in the solution 

 increases the dielectric constant, or at any rate the ionizing power of 

 the solvent. All of these theories are plausible, but it is highly improb- 

 able that neutral salt action is due to any one cause exclusively. 



l Journ. Amer. Chera. Soc. 31, 403, 886 (1909). =Zeit. phys. Chem. 4, 226 (1889). 

 2 /Wd., 35, 396 (1913). 



