IOWA ACADEMY Oi< SCIENCES. 



13 



kuowu principles this dissociatiou must become more complete with increas- 

 ing dilution, and of course the formation of colorless ions from the colored 

 salt must i-esult in a diminution of the intensity of the color. 



There is, however, another explanation not only possible, but probable. 

 Ostwald has shown that other salts of ferric iron, undergo in dilute solution 

 more or less complete hydroly&is into colloidal ferric hydrate and free acid. 

 If this hydrolysis also occurs in solutions, as we have no reason to doubt, 

 of the sulphocyanate, in accordance with the equation. 



Fe (SCN)3+3 H., 0=Fe (O H)3+ 3 H S C N, 

 It would offer a complete explanation of the phenomena hitherto observed. 



II. EXPEKIMENTAL PART. 



In order to obtain further insight into the nature of the changes occurring 

 upon dilution of solutions of ferric sulphocyanate, and indirectly of solu- 

 tions in general, it seemed advisable to operate in solutions containing no 

 water. 



In such solutions the hydrolysis called for by the second theory given 

 above could rot occur and the electrolytic dissociation called for by the first 

 theory could occur only in a subordinate degree. Hence both theories would 

 lead us to expect that a solution of stated concentration of Fe (SCNjg in 

 ether or in amyl alcohol or in absolute ethyl alcohol would have a much 

 more intense color than a solution of the same strength in water, and 

 second that the color would be proportional to the strength. 



My observations have coutirmed the tirst prediction, but not the second. 



A solution in ether was tirst prepared containing 4.7 m. g. Fe (S C N)^ 

 per cu. cm., both the iron and sulphocyanogen being dii*ectly determined 

 and found in accordance. From this solution, which was kept in the dark, 

 the other solutions were prepared and their absorbtion coefficients deter- 

 mined by repeated observations in a Vierordt spectroscope with double sym- 

 metrical slit. 



/''m-s^.— Comparison of absorbtive power in amyl alcohol and water solu- 

 tions. A solution containing .0625 m. g. Fe (S C N)3 per c. c. of amyl alcohol 

 transmitted 42 per cent of light of wave length 587, or about the same 

 amount as an aqueous solution containing .247 m. g. per c. c, or nearly four 

 times as strong. 



I. Amyl alcohol containing .05 m. g. Fe (S C N)3 per c. c, T=15^. 



