18 Taylor, Hypoiodous Acid and Hypoiodites. 



which manifestly contains free iodine (carbon bisulphide 

 shaken up with it is coloured deep violet), gives no blue 

 colour with starch until the addition of a drop of alkali, or 

 until it has been exposed to the air for some time. If a 

 little of the mixture of the brown solution with starch is 

 poured into a shallow vessel, or is poured backwards and 

 forwards from one vessel to another, it soon turns blue.* 



Some time before obtaining the free hypoiodous acid 

 in the way described above, I had obtained what must 

 have been either the acid or a solution of its silver salt by 

 another method. It was pointed out by Dancer (Chem. 

 Soc. Journ., xv., 447) that hypobromous acid could be 

 obtained by the action of bromine-water upon solution of 

 nitrate of silver, according to the following equation: — 



Ag N 3 +Br 2 +H 2 0=Ag Br-f-H O Br+H N O s . 



Chlorine acts in a similar way, producing hypochlorous 

 acid. A solution of nitrate of silver with powdered iodine 

 appears to form nothing but iodide and iodate of silver ; 

 but I found that iodine suspended in water gave a 

 bleaching liquid when shaken up with solution of silver 

 sulphate, or with a paste of silver carbonate, the carbonate 

 giving the better result. Wishing to obtain some quanti- 

 tative results, I began to use an aqueous solution of 

 iodine, instead of having it merely suspended in water. 

 Shaking up this solution with a little silver carbonate and 

 rapidly filtering, a liquid is obtained which contains a 

 small amount of silver, but which gives all the reactions 

 which I have described as characteristic of Schonbein's 



* Dr. A. Harden tells me that he has found that a mixture of aqueous 

 iodine and iodic acid, in certain proportions, behaves in exactly the same 

 way as the above solution. It is known that iodine forms no blue 

 compound with starch unless an iodide be present ; but I can offer no 

 explanation of the effect which the air appears to have on the above 

 reaction. 



