406 On ' Iodine. [J u ke, 



from the ratio of the oxygen of the iodine to that of the potassium; 



r 18817 . , 



for - = 5 very nearly. 



If we wish to have the quantity of hydriodate of potash which 

 corresponds to 100 of iodate, we must add to the 92*127 jjotassium 

 18-817 oxygen, and to the 293*940 iodine 2*497 hydrogen, which 

 saturate the oxygen of the potassium. Thus we obtain 407 "381 of 

 hydriodate. 



Iodate of Soda. 



The iodate of soda crystallizes in small prisms, usually united in 

 tufts. I have likewise obtained them in small grains seemingly 

 cubic. They deflagrate on burning coals like nitre, at a heat some- 

 what below a red heat ; but at the same time, a very small quantity 

 of iodine is disengaged. On this account the solution of the resi- 

 dual ioduret of sodium in water is slightly alkaline. 100 parts of 

 water at 58° dissolve 7'3 of this salt. It contains no water of crys- 

 tallization, and is not altered by exposure to the air. When decom- 

 posed by hea,t, it gives out 24*45 of oxygen, a result which does 

 not sensibly differ from the 24*43 of oxygen deduced from the pro- 

 portions of iodate of potash, and from the ratio of the oxidation of 

 potassium and sodium. I shall adopt this last number in preference, 

 and conclude from it that iodate of soda is composed of 



Oxygen 24-432 



Ioduret of sodium 75*568 



100-000 



On putting iodine into a solution of soda, so that the liquid was 

 upon the point of becoming coloured, 1 obtained by evaporation fine 

 crystals in sis-sided prisms, with bases perpendicular to the axis, 

 very alkaline, and deflagrating strongly upon burning coals. These 

 crystals are very soluble, and contain a great deal of water of crys- 

 tallization. As they were formed in the midst of a liquid containing 

 hydriodate of soda, chlorine produces in them a precipitate of 

 iodine. I consider them as a subiodate of soda. On adding soda to 

 a neutral solution of iodate of soda, I converted the whole into 

 crystals ; but instead of being bulky, like the preceding ones, they 

 were in small silky needles, united in tufts. They were not altered 

 by exposure to the air, though they were very alkaline. Potash 

 forms likewise an iodate with excess of base, and crystallizable. In 

 general, the iodic and hydriodic acids have a great tendency to form 

 subsalts. "v 



The iodates of potash and soda detonate by percussion, but very 

 feebly, when they are mixed with sulphur. It might be thought 

 that they could be employed v.ith advantage in the manufacture of 

 gunpowder. But a very simple calculation will show that nitre is 

 much preferable. 100 parts of nitre, when decomposed by heat, 

 give 53*62 of gas, while 100 of iodate give only 22*59. Therefore, 

 neglecting here the difference of density of azote and oxygen, and 



