\ 
POT 
cDiour. In the quantity of 5^, it renders 
mercury a fixed solid, of the colour of 
silver, and forms an alloy with tin, AVhen 
amalgamated with mercury, the amalgam 
will combine with other metals. 
Mr. Davy tried this with iron and pla- 
tina, and had reason to believe that these 
latter metals remain in combination with 
the mercury, even when deprived of the 
new substance by exposure to the aii'. 
From several curious and ingenious experi- 
ments to ascertain the proportions of the 
bases and oxygen in the two fixed alkalies, 
he concludes that 100 parts of potash con- 
sist of about 84 basik, and 16 oxygen; and 
100 parts of soda consist of about 76 or 77 
basis, and 24 or 23 oxygen ; or that potash 
may be considered as consisting of about 
6 parts basis, and 1 of oxygen ; and soda of 
7 basis, and 2 oxygen. In reply to the 
question, whether the bases of potash and 
soda should be called metals, it may be 
said that they agree with metals in opacity, 
lustre, malleability, conducting powers as 
to heat and electricity, and in their quali- 
ties of chemical combination. Even their 
low specific gravity does not appear a suf- 
ficient reason for making them a new class ; 
for amongst the metals themselves there 
are remarkable dift'arences in this respect, 
platina being nearly four times as heavy 
as tellurium; and tellurium is not much 
more than six times as heavy as the basis of 
soda. Conceiving the basis of the two 
fixed alkalies to be metals, Mr. Davy has 
named one Potasium, and the other Sodium ; 
adopting tiiat termination which, by com- 
mon consent, has been applied to other 
newly discovered metals. 
On an examination of the volatile alkali, 
and after a great number of complex 
and tedious experiments, Mr. Davy saw 
reason to conclude that ammonia contains 
oxygen as an essential ingredient, and that 
this cannot well be estimated at less tlian 
7 or 8 parts in the hundred : this body may 
therefore, as he sa)'s, be considered as the 
principle of alkalescence, with as much 
reason as the Frencli have made it the 
principle of acidity. After making some 
general remarks on the preceding facts, 
lie suggests the probability that the mu- 
riatic, fluoric, and boracic acids, all con- 
tain oxygen as one of their constituent 
principles. The earths of , barytes and 
strontian, as being most analogous to the 
alkalies, were likewise examined, and both 
yielded oxygen. In concluding this very 
important commnnicalion, Mr. Davy le- 
POT 
marks that an immense variety of objects 
of research is presented in tlie powers and 
aflinities of tiie new metals produced from 
the alkalies. In tliemselves they will un- 
doubtedly prove powerful agents for ana- 
lysis; and having an affinity for oxygen, 
stronger than any other known substances, 
they may possibly supersede the applica- 
tion of electricity to some of the unelecom- 
poimded bodies. Further experiments, it 
is said, have enabled Mr. Davy, since Ins 
commnnication to the Royal Society, from 
which tlie above has been partly abridged, 
to decompose in the most satisfactory man- 
ner, the barytes and strontites, and to show 
tliat the otlier alkaline earths are oxides of 
highly combustible metals. It cannot now 
be doubted that, in the hands of this great 
cliemist, other bodies, hitherto, deemed 
simple, or at least never yet analysed, will 
speedily yield to the powers either of the 
liiglily inflammable metals already discover, 
ed, or of a still further increase of the gal- 
vanic battery. Mr. Davy has decomposed 
carbonic acid by means of tliose metals, and 
has oxydated them by muriatic acid ; and 
an excellent writer says, “ it is now by no 
means improbable tliat charcoal itself hi- 
therto regarded as the most refractory 
of all substances, may be decomposed by 
the new instruments ; and that the means 
of obtaining it pure, and even clirystallized, 
shall at last be found ; a discovery which 
would enable art to vie with nature in the fa- 
brication of her most valuable produce.” At 
any rate to use the words of the Professor 
himself : “ In sciences kindred to chemis- 
try, the knowledge of the nature of the al- 
kalies, and the analogies arising in conse- 
quence, will open many new views ; they 
may lead to the solution of many problems 
in geology, and show that agents may have 
operated in the formation of rocks and 
earths, which have not hitherto been suspect- 
ed to exist.” See PhilosophicalTransactions 
of the Royal Society for 1808. Part I. 
POT s’.one, in mineralogy, a species of 
the Clay genus. The colour of this mineral 
is a greenish grey of different degrees of 
intensity. It occurs massive. The internal 
Instre is glistening and pearly. Fracture, 
sometimes curved, foliated, sometimes im- 
perfectly slaty. It Is soft, feels greasy and 
difficultly frangible. It is found in beds 
with serpentine, at Como in the Grisons ; 
in some parts of Saxony, and in Hudson’s 
Bay. It is very nearly allied to indurated 
talc. It is refractory in the fire and may 
be used for iining furnaces. It may be 
