388 IODINE. 



on the iodiferous mineral waters of the Andes.* It appears 

 to have a specific action in causing the absorption of 

 glandular swellings, and is also administered as a tonic. Iodine 

 swallowed in the solid state may cause ulceration of the mucous 

 membrane of the stomach, and death. But the iodide of potas- 

 sium or sodium is not poisonous in large doses, nor is the iodide 

 of starch hurtful (Dr. A. Buchanan). 



Iodides. Iodine does not form a hydrate like chlorine, but 

 it combines with another compound body, ammonia \ dry iodine 

 absorbing dry ammoniacal gas and running into a brown liquid, 

 which Bineau finds to contain 20.4 ammonia for 100 iodine, 

 quantities in the proportion of 3 equivalents of ammonia to 2 

 of iodine.f This liquid dissolves iodine. Iodine does not com- 

 bine with dry iodide of potassium, but with the addition of a 

 small quantity of water, it forms what appears to be a ternary 

 compound of iodide of potassium, water and iodine, which is 

 fluid, but was obtained in crystals by Bauer. It forms similar 

 combinations with other hydrated metallic iodides. With the 

 metals generally iodine combines, with the same facility, and 

 nearly with as much energy as chlorine does. The iodide of zinc 

 and protiodide of iron, which are very soluble, are formed by 

 simply bringing the metals into contact with iodine, in water. 

 All the iodides are decomposed by bromine, as well as by chlo- 

 rine. 



The compounds of iodine may be shortly described in the 

 following order: 



Hydriodic acid . H I 



lodic acid . . . I O 5 



Hyperiodic acid . I O 7 



Iodide of nitrogen N I 3 



Iodide of sulphur 

 Iodides of phosphorus 

 Chlorides of iodine. 

 Bromides of iodine. 



COMPOUNDS OF IODINE. 



Hydriodic acid, H I. Hydriodic acid cannot be prepared with 

 advantage by treating the iodide of sodium or potassium with 

 hydrated sulphuric acid, as the latter is partially converted into 

 sulphurous acid by hydriodic acid, with the separation of iodine. 

 It may be obtained in the state of gas, by forming an iodide of 

 phosphorus, 9 parts of dry iodine and 1 of phosphorus being 

 introduced into a tube sealed at one end, to be used as a retort, 



* An. de Ch. et de Ph. t. 54, p. 163. t An. de Ch. et de Ph. t. 67, p. 226. 



