Oxymuriatic Gas and Oxygen, Se. 405 
form a gray coherent mass, not fusible at a dull red heat, 
and which gives hydrogen by tue action of water. 
Whether these are trae prot-oxides, or merely mixtures 
of the alkaline metals with the alkalies, or with the alkalies 
and reduced silex from the glass, ] shall not at present at-. 
tempt to decide. 
. Potassium, L find, heated in a similar manner with fused 
potash, in a tube of platina, gives, after having been ignited, 
a dark mass that efferyesces. with water; but even in this 
case it may be said that the alloy of platina and potassinm 
interferes, and that the substance is. not a prot-oxide, but 
merely dry alkali mixed, with :this.alloy. 
As the pure alkalies were unknown till the discovery of 
potassium and. sodium *, and as their properties have never 
been described, it will. perhaps be proper, in, this place to 
notice, them hyellys c'gily tap. 994i Le 
When potassium and sedium are. burnt in.oxygen gas 
upon platina, and. heated to,redness to decompose the per- 
oxide of potassium, the, alkalies are of a grayish green co- 
lour... They are harder. than. common potash or soda, and, 
as, well as i.could determine, by an, imperfect, trial, of greater 
specific gravity.’ ‘They require, a_strong red beat for their 
perfect fluidity, and evaporate. slowly, by a still further in- 
crease of temperature, . When small quantities of water are 
added to.them, they heat violently, become white, and are 
converted into hydrats, and.then are easily fusible and vo- 
latile. sake hathveiooi iin Pen AN 
When potassium or sodium is burnt on glass, freed from 
metallic oxides, and strongly. heated, or,when potash or soda 
is formed from the metalsby. the action of a minute quan- 
tity of water, their colour approaches to white but in other 
scusible ;properties they resemble, the alkalies: ormed upon 
metallic substances; and are. distinguished in a_ marked ; 
manner by their difficult fusibility from the potash and soda 
DIAD Asem by, alcObole ts hc. sam ctulin ite. hacen ine yas 
_M. D’Arcet and. more distinctly M.Berthollet have con- 
Ra Stahl spptaached nearly to, the discovery of the pure alkalies. He ce- 
mented solid caustic potash With iron filings in a’ long’ continuéd heat, and 
states, that in this way an alkali “ valde causticum’”?is produced. Specim. 
Bech. part ii, page 255. He procured caustic allali also, by decomposing 
nitre by the metals... Jd. p. 253. 
! find that when nitre is decomposed in a crucible of platiia, by a strong 
red heat, a yellow substance remains, which consists of potash ard oxide of 
platina, apparently in chemical combination. ‘IS he undecompounded potash 
which comes over in the process for procuring potassium by the gun-barrel, 
is of an olive colour, and affords oxide of iron during its solution in waters 
Pure potash Will probably be found to have an affinity for many metallic 
* oxides. 
ai) Cc3 cluded 
