1815.] On lodhie. 407 



ol)serving that oxygen in the detonation of gunpowder is cluefly 

 employed in the production of caibonic acid gas, the volume of 

 which is equal to its own, nitre has the advantage, every thing else 

 being equal, of giving 2*3 times as much gas as it. It is possible, 

 however, that the detonation of powder made witii the iodate may 

 be more rapid than that of powder made with nitre. 



lodaie of Ammonia, 



We can only obtain this salt by saturating with ajnmonia iodic 

 acid, or the solution of chloruret of iodine. It is in small gra- 

 nular crystals, the shape of which 1 have not been able to ascertain. 

 When thrown upon burning coals, or upon a hot body, it detonates 

 with a hissing noise, giving out a weak violet light and vapours of 

 iodine. I endeavoured to decom})Ose it by Ijeat in a glass tube, but 

 it broke the apparatus. I collected, however, enough of the gas 

 evolved to ascertain that it was a mixture of oxygen and azote. 

 When we calculate its composition from the preceding data, we 

 find it composed of 



Iodic acid 1 00-00 



Ammonia lO'Dt 



But 100 iodic acid contain 75*80 of iodine; and if we reduce 

 this quantity to volumes by dividing 75'80 by 8 6 IDS, the specific 

 gravity of iodine in vapour we find 8'79i. If we divide 10*94 by 

 0-59669, the specific gravity of ammonia we find 17'587j which is 

 the double of 8-794. Hence iodate of ammonia is composed in 

 volume 



Ammoniacal gas 2 



Vapour of iodine 1 



Oxygen gas 2*5 



The two volumes of ammoniacal gas give, when they are decom- 

 posed, one volume of azote and three of hydrogen. The hydrogen 

 requires for its saturation 1"5 oxygen. There then remains one 

 volume of oxygen, or a bulk equal to that of the azote. On deto- 

 nating iodate of ammonia, I have obtained the two gases in nearly 

 tliat proportion. 



Iodate of Barytes. 



We obtain it very easily, either by double affinities, or by putting 

 iodine into barytes-watcr. It precipitates in powder, which is ob- 

 tained pure after being several times washed. This salt, while 

 drying, concretes into lumps, and becomes mealy, 'i'hough kept 

 fur a long time in the temperature of 'J 12°, it gives out water before 

 being decomposed by heat ; so that it seems to retain water in com- 

 bination, 'i'he products of its dccom|X)silion are oxygen, iodine, 

 and barytes, sensiljly pure. This barytes dissolves very slowly in 

 water; and as it retains no iodine, though that which is oljlained by 

 the decomposition of the nitrate combine with it, I presume that tlvc 



