Roberts — Action of Reducing Agents on Iodic Acid. 151 



were freed as far as possible from air by boiling in water for 

 some time and transferring them while still wet to the gene- 

 rator. The gas was washed with a dilute solution of sodium 

 carbonate. "With very refractory minerals the strongest hydro- 

 fluoric acid that is available, mixed with about one-fifth its 

 volume of concentrated sulphuric acid, should be used, in 

 most cases, however, dilute acids are sufficient and much more 

 convenient. Occasionally there is a tendency for the mineral 

 to settle on the bottom of the crucible and cause bumping, 

 but this can usually be prevented by addition of some coils of 

 platinum wire. 



In conclusion, the author takes pleasure in expressing to 

 Professor Penfield his ttianks for valuable advice and assistance. 



Laboratory of Mineralogy and Petrography, 

 Sheffield Scientific School, New Haven, April, 1894. 



Art. XXI. — The Action of Reducing Agents on Iodic Acid / 

 by Charlotte F. Eoberts. 



[Contributions from the Kent Chemical Laboratory of Tale College — XXXL] 



I. The Absorption of Nitric Oxide by Iodic Acid. 



The following investigations were first undertaken with the 

 object of studying the solubility of nitric oxide in iodic acid. 

 Although most chemical authorities agree in the statement 

 that nitric oxide is absorbed by iodic acid with the separation 

 of iodine, there is a certain indefmiteness with regard to the 

 degree of solubility, which led me to investigate the subject 

 for myself. Thus, Gmelin-Kraut states that " All the lower 

 oxides of nitrogen decompose iodic acid into iodine and nitric 

 acid, but the decomposition takes place only in presence of a 

 considerable quantity of water," but the degree of ease with 

 which the decomposition takes place meets with no comment, 

 and the " considerable quantity of water " seems a somewhat 

 indefinite condition. Hammerer,* who is the authority re- 

 ferred to for the above facts, and who, some years ago, made 

 a thorough study of iodic acid, says, without referring to any 

 illustrative experiments, " At ordinary temperature, I 2 6 is 

 reduced only in aqueous solution by nitric oxide, but this gas 

 is without action upon the water-free acid and its solution in 

 concentrated sulphuric acid. At 100° the latter is very slowly, 

 the water-free acid not at all decomposed." 



A portion of this latter statement was very easily verified. 

 Some nitric oxide was passed through the dry acid, and other 



* Jour, fur prak. Chem., lxxxiii, 73. 



