IODIC ACID. 391 



after reddening, bleaches litmus paper. It oxidates all metals 

 with which it has been tried, except gold and platinum. It is 

 deoxidized by sulphurous acid, and iodine liberated, but an 

 excess of sulphurous acid causes the iodine again to disappear 

 as hydriodic acid, water being decomposed by the simultaneous 

 action of sulphurous acid and iodine upon its elements. Mor- 

 phia is said to be the only vegetable alkali which decomposes 

 iodic acid and liberates iodine ; and, hence, iodic acid has been 

 recommended as a test for morphia. 



lodates. The salts of iodic acid have a general resemblance 

 to the chlorates. The iodate of potash is converted by heat into 

 iodide of potassium and oxygen; but the iodate of soda loses 

 iodine as well as oxygen, when heated, and a yellow, sparingly 

 soluble, alkaline matter remains, which Liebig imagines to con- 

 tain the salt of an iodous acid, resolvable into an iodate and 

 iodide by solution in water, but which requires further investi- 

 gation. The iodates of metallic protoxides, with the exception 

 of the potash family, are all sparingly soluble or insoluble salts. 

 The iodate of lime contains water, and when heated affords no 

 iodide of calcium, but caustic lime. 



Fixed acids, which have little affinity for water, such as iodic 

 acid, appear often to combine in several proportions with oxides 

 of the potash family. The ordinary biniodate of potash contains, 

 I find, an atom of basic water, but at a high temperature it is 

 made anhydrous, and then a salt remains containing two atoms 

 of acid to one of potash. Mr. Penny has crystallized a biniodate 

 and teriodate of soda, both anhydrous. 



Iodic acid likewise combines with other acids, an observation 

 of Davy's, which was disputed, but has been confirmed by Ber- 

 zelius.* These are compounds which generally precipitate in a 

 crystalline form, when another acid is added to a hot and con- 

 centrated solution of iodic acid. Compounds of sulphuric, 

 nitric, phosphoric and boracic acids with iodic acid were formed 

 by Berzelius. The compound with sulphuric acid may be sub- 

 limed without decomposition. When vegetable acids are dis- 

 solved in iodic acid, they are immediately decomposed by it, 

 carbonic acid being disengaged with effervescence and iodine 

 precipitated. 



Hi/periodic or Periodic acid, I O 7 . This acid, which was 



Traite tie Chimie, t. I. p. 212. 



