A M M 



A M O 



The opinion at prefent entertained refpcfting the compo- 

 lition of ammonia is, that it is compofed of three volumes of 

 hydrogen and one volume of azote condenfed into two 

 volumes. Hence its fpecific gravity compared with that of 

 common air is .590 ; 100 cubic inches at a mean tem- 

 perature and preffure weigh 18 grains, and the weight 

 of its atom is 21.25 ; ^^^^ °^ oxygen being confidered 

 as 10. 



Ammoxia, Salts of. Thefe have been omitted in the 

 ufual place, namely, under Ammonia ; but moft of them will 

 be found in a fubfequent part of the \Tork, under Salts. 

 Thofe defcribed elfewhere will be referred to here, and thofe 

 remaining to be defcribed will be now noticed. 



Sulphite of Ammonia. See Sulphite of Ammonia, 



Chromate of Ammonia. This fait may be formed by 

 faturating chromic acid by ammonia. It ufually exifts in the 

 form of dendritical cryftals of a fine yellow colour. When 

 nightly heated, it is decompofed, even when in folution, 

 brown flocks of chromic oxyd precipitating. 



Arfeniate of Ammonia. See Arseniate of Ammonia. 



Molybdate of Ammonia, This fait diffolves readily in 

 water. The folution does not cryftallize. When heated, 

 the ammonia is partly driven off, partly decompofed, and the 

 acid is reduced to the ftate of an oxyd. 



Tungjlate of Ammonia. This fait may be formed by 

 diffolving tungftic acid in carbonate of ammonia. It is 

 foluble in water, and cryftallizes. Its tafte is metallic, and it 

 is entirely decompofed by heat. 



Benxoate of Ammonia. This fait cryftallizes with dif- 

 ficulty. It deliquefces, and is very foluble in water. It has 

 been recommended by Berzelius as an excellent re-agent for 

 precipitating iron from its folution. It throws down this 

 metal of an orange colour, and occafions no infoluble preci- 

 pitates with any of the other bafes, except tellurium and 

 mercury, and perhaps eopper, all of which are thrown down 

 whit£. 



Succinate of Ammonia. See Succinic Acid. This fait has 

 alfo been much recommended for precipitating iron when in 

 the ftate of peroxyd. 



Camphorate of Ammonia. This fait may be prepai-ed by 

 diffolving carbonate of ammonia in hot water, and adding 

 camphoric acid flowly till the alkali is faturated. It cryf- 

 tallizes with difficiJty ; is fparingly foluble in cold water, 

 but much more foluble in hot. It is completely foluble in 

 alcohol. Moft of the calcareous falts form triple compounds 

 with this fait. 



Citrate of Ammonia. See Citrate of Ammonia. The 

 remaining falts of ammonia are fo totally devoid of interell, 

 or fo little known, that we do not think it ncceifary to enu- 

 merate them. 



AMMYRSINE, in Botany, a new genus of Mr. Purfti's, 

 more happily circumftanced in its charafters, perhaps, than 

 in its name. The latter is formed from a/ji^oi, fand, and 

 (xu^(riv»i, a dwarf myrtle ; but Myrjine, being an eftablilhed 

 generic name, cannot, with propriety, make a part of 

 another. Linnianlaw, (fee Phil. Bot.feff. 225,) and good 

 fenfe, are both againft it ; and if fome fimilar innovations 

 have, from peculiar caufes, crept in, they are not to be 

 in-.itated, though for the prefent they may be tolerated. 

 The genus in queftion is founded on Ledum buxifolium, 

 (fee Ledum, n. 3,) and ftands in the Clafs and Order Pen- 

 tandria Monogynia, in Mr. Purlh's Flora 2 So and 301, 

 agreeing, of courfe, in Natural Order with Ledum. Tlie 

 foUovnng are its charafters. 



Calyx in five deep fegments. Petals five. Stamens 

 prominent. Capfule of five cells, burfting at the fummit. 



3 



Ledum is charailerized. 



Calyx minute, five-toothed. Corolla flat, in five deep 

 fegments. Capfule of five cells, burfting at the bafe. 



AMNIOS, Liquor of the. Chemical Properties of. Tiic 

 peculiar acid principle termed by Vauquelin and Buniva 

 amniotic acid, does not appear to exift during all the periods 

 of geftation in the liquor amnii of the cow. Dr. Prout 

 examined this fluid taken from an animal which had been 

 flaughtered in an early period of her geftation, hut was not 

 able to deleft any of the acid in queftion. See Annals ot 

 Philofophy, vol. v. p. 416. 



AMOMUM, in Botany, ajj-xf^ov of the Greeks, moft 

 probably derived from its Arabic denoinination hhamdmd, 

 as De Theis writes it, is the ancient name of a fort of 

 aromatic grain, or fruit, included, according to all appear- 

 ance, among the fpecies of the prefent Amomum of 

 botanifts. (See our former article, where this genus com- 

 prehends a much more extenfive range of fpecies than are 

 now underftood to belong to it.) Linnxus, and his imme- 

 diate followers, included under Amomum almoft every plant 

 of the Scitaminex that they knew not how otherwife to dif- 

 pofe of ; and Gaertner, though he altered the name for the 

 worfe, to Zingiber, (fee that article,) threw no new light 

 upon the cliarafters or hiftory of the genus, but rather, 

 like every body elfe, added to their confufion. Mr. Rofcoe 

 firft defined this genus, like the reft of the SciTAMiNEiE, as 

 the reader will find under that head, by a clear diftinftive 

 charadler ; and while he greatly reduced the number of 

 fpecies, rendered the whole perfeftly clear and intelligible. 

 We fliall, as we have done with Alpinia, give a full view 

 of this genus, as at prefent underftood, and while we make 

 confiderable retrenchments, fliall have fomething new to 

 add in their place.— Rofcoe Tr. of Linn. Soc. v. 8. 351. 

 t. 20. f. II. Dryandr. in Ait. Hort. Kevi'. v. i. 8. Linn. 

 Gen. 2. Schreb. 3. Willd. Sp. PI. v. i. 6. Mart. Mill. 

 Dift. V. I. Carey Hort. Bengal, i. Roxb. Monandr. 23. 

 Jufl". 63. Lamarck Illullr. t. 2. f. I. (Zingiber ; Gaertn. 

 t. 12. f. I, 2, 3. 6.) — Clafs and order, Monandria Mono- 

 gynia. Nat. Ord. Scitaminea, Linn. Cannnc, .lufl^. 



Gen. Ch. Cal. Perianth fuperior, of one leaf, tubular, 

 flieathing, membranous, coloured, fplitting at one fide about 

 half way down. Cor. of one petal ; tube thorter than the 

 calyx, cylindrical, eredl ; outer limb in three nearly equal, 

 oblong-lanceolate, concave, ereft fegments much longer 

 than the calyx ; inner of one large, undulated lip, with a 

 (hort concave claw. Stam. Filament one, rather longer 

 tlian the claw, ftout, oblong, deprefled, fomewhat incurved, 

 with a lanceolate, acute, afcending lobe, about half its own 

 length on each fide, at the bafe, and a pair of fimilar, ereft 

 or tranfverfe, lobes, forming a creft at the fummit, with 

 either an intermediate prominence, or a notch ; anther of 

 two diftinft, eUiptic-oblong, lobes, attached by the back, 

 below the fummit. Pijl. Germen inferior, fmall, roundifti, 

 fomewhat furrowed ; ftyle thread-ftiaped, lying clofe to the 

 filament, between the lobes of the anther ; ftigma funnel- 

 (hapcd, fringed, ereft, projefting a little beyond the filament. 

 Peric. Capfule either ovate-oblong, or nearly globular, of 

 tliree cells, and three coriaceous, fomewhat ftriated, valves ; 

 the partitions membranous. Seeds numerous, oblong, round- 

 ifti, or (lightly angular, each enveloped in a foft: pulpy 

 tunic, which becomes membranous, or evanefcent, when 

 dry. 



Eff. Ch. Anther of two diftinft lobes. Filament with 

 a lobed creft, above the anther. Outer limb of the corolla 

 in three oblong lobes ; inner a fingle lip. Capfule of three 

 cells and three valves. Seeds tunicated. 



One of the moft natural genera tliat can exift, in any 

 natural order, and the bell defined in habit, as vVell as 



charafter. 



