PET 
PET 
771 
platinum, it a£Vs on it. It has a ftrong affinity for acids, 
and a very high neutralizing power, even furpaffing that 
of magnefia. Placed in the voltaic circuit, Sir H. Davy 
ffiowed that it was decoinpofed with the fame phenomena 
as the other alkalies. A portion of its carbonate being 
fufed in a platinum capfule, the platinum was rendered 
pofitive, and a negative wire brought to the upper furface. 
The alkali decompofed with bright fcintiilations, and the 
reduced metal, being feparated, afterwards burnt. The 
final 1 particles which remained a few moments before 
they were reconverted into alkali, and allowed a ffiort ex¬ 
amination, were of a white colour, and very fimilar to 
fodium. A globule of quickfilver made negative, and 
brought into contaCt with the alkaline fait, foon became 
an amalgam of lithium, and had gained the powerof act¬ 
ing on water, and evolving hydrogen, an alkaline folu- 
tion refulting. 
The chloride of lithium obtained by evaporating the 
muriate to drynefs, and fufing it, is a white femi-tranfpa- 
rent body, analogous in its appearance to the chlorides of 
potaffi and foda, but very different from them in its ge¬ 
neral properties. It is extremely deliquefcent, whereas 
they are not fo : in this refpecl it almoft equals muriate 
of lime. Its folution cryftallizes with great difficulty, 
but by evaporation affords minute needle-form cryftals. 
It is very foluble in alcohol; but the chlorides of potaffi 
and foda very little fo. Its folution, or the moift fait, has 
the property of tinging the flame of alcohol of a fine red, 
fomewhat like ftrontian, but the other alkaline muriates 
have not this power. It fufes below a red heat; and, when 
heated powerfully in the open air, it gradually lofes 
chlorine, abforbs oxygen, and becomes ftrongly al¬ 
kaline. 
All its falts are very fufible, but in fome cafes a Angular 
degree of infolubility belongs to them. The nitrate is a 
very foluble fait, deliquefcent, and capable of cryffaliifing 
in rhomboids. It has a very aigre tafte: heated, it rea¬ 
dily fufes, and is then decompofed with the fame pheno¬ 
mena as nitre. 
The fulphate of lithia is a fait which cryftallifes readily 
in fmall reftangular prifms; they are perfectly white, and 
poffefs much lultre ; have a faline tafte, very different from 
potaffi or foda ; are more foluble in water than fulphate 
of potaffi; perhaps not fo foluble as fulphate of foda: 
the cryftals contain no water; they fufe and become very 
liquid below a red heat; their folution does not preci¬ 
pitate the muriate of platina, nor is it precipitated by 
tartaric acid. M. Vauquelin gives an experiment on its 
conftitution, the refult of which is as follows : 
Sulphuric acid .... 69.18 
Lithia.30.82 
100.00 
The fub-carbonate of lithia is but little foluble in 
water, and tfflorefces in the air. It may even be preci¬ 
pitated from its fulphate by adding a ftrong folution of 
carbonate of potaffi to it. It is readily fufible ; and, when 
fufed, requires repeated additions of water with boiling 
to diffolve it again. Cold water difi’olves about one 
one-hundredth part of its weight of this fait; and the fo¬ 
lution aCts powerfully on vegetable colours, and eft'er- 
vefces with acids. According to Vauquelin, it attracts 
carbonic acid very rapidly from the atmof'phere. The 
carbonate, heated on platinum, a< 5 ts on it almoft as pow¬ 
erfully as the fixed alkaline nitrates. It feparates am¬ 
monia from its combinations, but is decompofed by lime 
and barytes, and rendered cauftic. The folution of the 
carbonate precipitates the muriate of lime, the fulphates 
of magnefia and alumina, and the falts of copper, fllver, 
and iron, juft as the other alkaline carbonates do; but it 
does not precipitate the muriate of platinum, as is the 
cafe with the fub-carbonate of potafh. 
With refpeCt to the proportions of the elements of the 
Vol. XIX. No. 1342. 
alkali, they do not appear exaCtly determined. M. 
Arfwedfon ftates, that lithia contains 43.9 per cent. of 
oxygen; M. Vauquelin concludes that It contains 44.-84 
per cent. See Journal of Science, N° 10. and London 
Med. Journal, vol. xl. p. 109 and 134. 
PETALO'MA, f [fo named by Swartz; from the Gr. 
7t(Iol\ov, a petal, and tou.a., a border; becaufe the petals are 
inferted into the margin of the calyx, between its teeth.] 
In botany, a genus of the clafs decandria, order mono- 
gynia, natural order of calycanthemse, Linn, (onagrae, 
jnff.) Generic characters—Calyx: perianthium fupe- 
rior, of one leaf, cup-lhaped, permanent, with five acute, 
equal, flightly-fpreading, teeth. Corolla: petals five, ob¬ 
long, fpreading; their claws inferted between the 
teeth of the calyx, deciduous. Stamina : filaments 
ten, inferted into the rim of the calyx, longer than the 
corolla ; antheras oblong, incumbent, opening by two 
pores at one end. Piftillum : germen inferior, ovate; 
ftyle elongated, awl-fhaped; ftigma Ample, acute. Peri- 
carpium : berry globofe, flefhy, crowned by the calyx, of 
one cell. Seeds from one to four, angular on one fide, 
convex on the other. — EJJential Charatter. Calyx 
pitcher-fliaped, five-toothed ; petals five, inferted between 
the teeth of the calyx; ftamens inferted into its border; 
berry of one cell. It is feparated from Myrtus, on ac¬ 
count of the form of the calyx, and the infertiori of the 
ftamens. There are two fpecies. 
1. Petaloma myrtiiloides, or filver-vvood ; ( Swartz. 
Prodr. 73. Ind. Occ. 833. Myrti-folio arbor, cortice 
argenteo, Sloane Jain. t. 187. f. 3.) Stalks folitary, fingle- 
flowered; leaves nearly ieffile, ovate, taper-poinfed, 
oblique at the bafe. Native of Hifpaniola and Jamaica, 
in low woods. Swartz defcribes it as a fhrub, two or 
three feet high ; Sloane fays the trunk is twenty feet in 
height, ftraight and undivided. Both agree that the bark 
is fpotted with white, whence arofe the Englifh name. 
The leaves are oppofite, entire, thin, fmooth, and ino¬ 
dorous, one and a half or two inches long. Flowers ax¬ 
illary, folitary, rarely oppofite, on fhortifh (talks, white, 
fmaller than a currant-blofl’om, but with long projecting 
ftamens and ftyle. Berry ovate, crowned with the ca- 
jyx, black and fhining when ripe, with feldom more than 
one feed. The afpeCt of the whole plant is like fome fpe¬ 
cies of myrtle; but it wants the ftrong tafte and fmell of 
that genus, and the ftruCture of the flowers is totally-dif¬ 
ferent. 
2. Petaloma mouriri, ( Sw . Ind. Occ. 835. Mouriri 
Guianenfis, Anbl. Guian. 1.180.) Stalks cluttered ; leaves 
(talked, broad-ovate, pointed ; berries with four feeds. 
Native of woods in Guiana, near the river of Sinemari, 
where Aublet found it flowering in November, and bear¬ 
ing ripe fruit in January. The trunk of this tree is 
thirty or forty feet high, and eighteen inches in diameter, 
bearing at the top numerous branches, fpreading in every 
direction. The bark is grey ; the wood whitifh, hard, 
and clofe-gramed. Leaves longer, and much broader, 
than thofe of the foregoing, as well as of a firmer texture; 
paler underneath, but fmooth and fhining on both (ides. 
Footftalks fhort and thick. Fiower-ftalks axillary, clut¬ 
tered, and fomewhat umbellate, with fmall, oppofite, 
acute braCtes. Flowers yellow ; berry yellow, minutely 
dotted with red, containing four feeds. Nothing is re¬ 
corded of the qualities or ule of this tree ; but the inha¬ 
bitants of the country where it grows name it mouririchira. 
PETALOS'TEMUM, /. in botany, fo called by Mi- 
chaux, from the Gr. vrelaAor, a petal, and r*'iy.wv, a ftamen; 
on account of the union of thofe two parts.of the flower 
into a tube. See Dalea. 
PET'ALOUS, or PEtalloid, adj. Having petals. 
PETAMI'NARIUS, J'. in antiquity, a name given to 
certain perfons who performed extraordinary feats of ac¬ 
tivity; took perilous leaps, vaults, &c. The word is 
formed from the Gr. mi}ay.cn, I fly; but fome authors 
write it pctiminarius ; and derive it from petimen, which, 
9 L according 
