OXYGENATED COMPOUNDS OF IODINE. 359 



2. If iodine be dissolved in diluted potash, at the ordinary 

 temperature, with the aid of the crusher described in p. 247, 

 two thermal effects succeed each other very rapidly. During 

 the first minute a lowering of the temperature is observed, which 

 reaches 0'30 when we dissolve, for instance, 31 grms. of iodine 

 in 500 cc. of a solution containing one quarter of an equivalent 

 of potash per litre. 



This initial phenomenon corresponds to the solution of the 

 greater portion of the iodine employed. Effects of the same 

 sign take place with solutions twice and four times as diluted. 

 As soon as these effects are produced the thermometer begins to 

 rise again in consequence of a new reaction, which lasts four to 

 five minutes, while the whole of the iodine becomes dissolved. 

 All the reaction can be effected with equivalent proportions 

 (excepting a trace of free iodine or some other compound which 

 turns the liquor slightly yellow). At this moment the solution 

 contains potassium iodate and iodide, according to the well- 

 known reaction 



3I 2 + 3K 2 (diluted) = 6KI (dissolved) + KIO 3 (dissolved). 



3. It may be that the initial phenomenon is due to the 

 formation of a hypoiodite 



I 2 + K 2 (diluted) = KIO (diluted) + KI (diluted) ; 



but this body has only a momentary existence, and is changed 

 forthwith into iodate at the ordinary temperature. 



4. It is well known that the same reaction with the hypo- 

 chlorites is only produced very rapidly at 100. 



The hypobromite, with an excess of alkali, resists much 

 longer, as has been proved. 



5. This unequal stability of the three salts is explained by 

 the inverse progression of the stability of the chlorates, bromates, 

 and iodates, as will be seen by-and-by. Free hypochlorous acid 

 is, on the contrary, the most stable of all ; for it can be dis- 

 placed unchanged when cold by carbonic acid, and even by 

 acetic acid, whereas either of the latter acids, when in presence 

 of the hypobromites, separate the bromine at once, as Ballard has 

 observed from the beginning. This bromine is probably mixed 

 with some other compound, as was ascertained from the 

 measurement of the heat liberated. 



6. Let us, however, return to the formation of the hypoiodite. 

 When iodine is added to diluted potash in successive fractions 

 for instance, in twice or three times each addition gives rise to 

 the same succession of phenomena, namely, to a lowering of 

 temperature, immediately followed by an increase of heat; 

 which shows that the effect is very characteristic of the reaction 

 itself, and independent of the fractions of iodine and potash 

 already combined. These singular effects, which only the 



