* 
‘ 
Oxymuriatic Gas and Oxygen, Se. 409 
heated in vacuo before the combustion, to decompose the 
water in the crust of potash; for im cases when this pre- 
caution was not taken, I found that hydrat of potash sub- 
limed, and lined the upper part of the retort, and from this 
the oxymuriatic gas separated water as well as oxygen. 
The phznomenon of the separation of water from hydrat 
of potash by oxymuriatic gas, was happily exemplified in an 
experiment in which [ introduced oxymuriatic gas to the 
peroxide of potassium, formed in alarge retort, and in which 
the potassium had been covered with a considerable crust of 
hydrat of potash. The upper part of the retort and its neck 
contained a white sublimate of hydrat, which had risen in 
combustion, and which was perfectly opake. As soon as 
the gas was admitted, it instantly became transparent from 
the evolution of water 3; and on heating the glass in contact 
with the sublimate, its opacity. was restored, and water 
driven off, : y otboos sti an tril 
In various.:cases in which I heated:dry potash, or mix- 
tures of potash and the peroxide, in oxymuriatic gas, there - 
‘was no separation of moisture, except when the gas con- 
tained aqueous vapour; and the oxygen evolved in the pro- 
cess, when the heat was strongly raised, exactly correspond 
ed to that absorbed by the potassium. | 
225 cubical inches of inflammable gas were collected, and 50 grains of potas- 
sium, and a large quantity ofan alloy of potassium and iron formed, so that 
it is scarcely possible to doubt that all the hydrogen produced from the de- 
composed hydrat:of potash) was liberated. 
_ Mr. Dalton conceives.that there iis an analogy, between potassium and so- 
dium, and the compeundsiofhydrogen..with sulphur, phosphorus, and arse- 
nic; but Iam atlossto trace any similarity between sulphuretted hydrogen, 
“ which is a,gaseous body, sqlublein,water, and haying acid pro serties; and a 
highly inflammable solid, metal which,produces alkali by combustion. Po- 
tassium might ias well be; compared to carbonic acid, Mr. Dalton consi- 
ders the volatility of potassium and sodium as favouring the idea of their 
containing hydrogen; but: they, are; less volatile than antimony, arsenic, and 
tellurium, and much less; volatile, than, mercury. He mentions their low 
specific gravity as a-cireumstance fayourable.to this idea. Ihave on a for- 
mer occasion examined. this argument, first brought forward by M. Ritter; 
but it may not beamissto.add, that if potassiumis a compound of hydrogen 
and potash, hydrat of potash must contain an equal quantity of hydrogen, 
with the addition of alight gaseouselement, oxygen, which might be expected 
to diminish rather than to inerease.the specific gravity of the compound. 
Mr. Dalton states, p. 488, that potassium, forms dry hydrat of potash, by 
decomposing nitrous gas and nitrous oxide: this is not the case: and he does 
not refer to experiment. I find by some very careful trials, that potassium 
attracts the oxygen and some of the nitrogen from these bodies, and forms a 
fusible compound which may be decomposed, giving off nitrogen and its 
excess of oxygen, by a red heat, and, which becomes polash, and not dry hy- 
drat of potash. t 3 
MM. Gay Lussac and Thenard have convinced themselves that potassium 
and sodium are not hydrurets of potash and soda, by a method similar to 
that which I adopted and published some months before, namely, by pro- 
ducing neutral ealts from them. When 
