and Observations on Iodine, 
497 
that the alkaline property which I at first supposed to belong 
to the compounds of potassium and sodium with iodine, de- 
pended upon some imdecomposed subcarbonate of potassa 
mixed with the hydrate of potassa I employed, as the subcar- 
bonate of potassa is decomposed by iodine and carbonic acid 
set free, I had not thought it probable that the sUbcarbonate 
of potassa could interfere with this result. But I find that if 
the subcarbonate exist at all in the lixivium, a poriion of it 
always remains undecomposed. I find likewise, that when a 
solution of iodine in lixivium of potassa is rendered perfectly 
neutral, or even slightly acid by hydroionic acid, a strong red 
heat renders the solid substance obtained slightly alkaline, 
provided it be in contact with air. Whether the separation'of 
iodine by oxygene, in this instance, depends upon some effect 
of the moisture contained in the atmosphere, or upon the con- 
tinued action of fresh portions of oxygene on the same surface 
of the compound, it is not easy to say ; but a similar effect I 
find is produced upon potassile, (fluate of potassa ;) this substance 
gains the power of reddening paper tinged with turmeric, by 
being strongly heated in contact with the air. 
The power of neutralizing acids does not belong to the true 
compound of iodine and potassium, but depends either upon 
the subcarbonate not decomposed, or upon the alkali formed 
during the ignition of the compound ; the pure double com- 
pound seems to have no power of action on the acids it does 
not decompose ; I fused it in contact with sulphurous acid gas 
confined by mercury in a glass tube, the salt gained a slight 
tint of yellow, but did not absorb its own volume of gas ; 
after this, it slightly reddened litmus, so that the acid must 
have had little more than a mechanical adhesion to the salt. 
