1815.) Philosophical Transactions, 1814, Part IT. 137 
oxygen. When iodine is dissolved in potash or soda, two com~- 
pounds are formed ; one composed of oxygen, iodine, and potas- 
sium or sodium; the other of iodine and potassium or sodium. 
Our author calls the first oxiode of potassium, &c. the second 
iode of potassium, &c. When the alkali is saturated with iodine 
crystals are deposited. These are to be digested in alcohol of 8-6, 
or 9:2. The undissolved portion is the triple compound. Oxiode 
of potassium is almost tasteless, has no action on vegetable colours, 
is scarcely soluble in cold water; but more so in hot water. By 
heat it may be dissolved in sulphuric, nitric, and phosphoric acids. 
The saturated solutions congeal and form crystalline masses of an 
intensely acid taste. When strongly heated the triple compound is 
decomposed at the temperature at which the acids are driven off 
and oxygen and iodine exhales. Oxiode of potassium dissolves 
readily in phosphorous acid. When the solution is heated the acid 
is converted into the phosphoric, and iodine appears. | When 
thrown into muriatic acid, an effervescence is perceived, the smell 
of chlorine becomes sensible, and the fluid, when evaporated, yields 
chlorionic acid. Similar appearances take place with the vegetable 
acids and the oxiode ; all easily explained by the transfer of oxygen 
to the solvent. 
Sir H. Davy conceives oxiode of potassium to be composed of 
one atom iodine, one atom potassium, and six atoms oxygen ;. but 
his experiments scarcely seem sufficient to warrant any such con- 
clusion. 
He formed likewise by a similar process, .oxiodes of barytes, 
lime, and magnesia. 
His attempts to obtain a compound of oxygen and iodine were 
not attended with success. 
2. On hydrionic acid and the compounds obtained by means of 
it. This acid is obtained pure by heating iode of potassium and 
hydro-phosphoric acid together. It is slowly decomposed by heat, 
and rapidly when heated along with oxygen gas. When condensed 
in water it is instantly decomposed by nitric acid-and iodine preci- 
pitated. It rapidly absorbs oxygen trom the air, and becomes 
yellow, and at last a deep tawny orange. It will probably answer 
well as a eudiometrical substance. It was decomposed by all the 
metals tried, except gold and platinum. With the alkalies and 
common earths it forms compounds very similar to those formed 
with the same bases by muriatic acid. 3. On other acid com- 
pounds of iodine. Iodine absorhs nearly one third of its weight of 
chlorine gas, and forms a very volatile compound, which acts upon 
mercury, and is dissolved by water. Sir H. Davy supposes that 
this compound is composed of an atom of iodine and an atom of 
ehlorine. He calls it chlorionic acid. Its colour is yellow, and it 
readily dissolves iodine becoming deeper coloured. When agitated 
in chlorine gas it becomes colourless. In this state, when poured 
into alkaline or earthy solutions, oxiodes are precipitated. If it be 
£oloured a quantity of iodine appears at the same time, When 
