ACE 



Acetic acid of tlie fp. gr. 1.063 '^ the ftrongeft that 

 can be procured. It cryftaUizes at the temperature of 55^, 

 awl the cryllals melt llowly when heated to 72^"^. This had 

 been long ago obferved by Courtenvaux. Lowitz has pro- 

 pofed an ingenious method of obtaining it of the requifite 

 degiee of ftrength to cryftallize. This confifts in making 

 diftilled vinegar into a thick pafte with well-burnt charcoal, 

 and expofing the mixture to a temperature of 2 1 2°. The 

 watery part is driven oft, and the acid remains. The acid 

 itfelf may be feparated by a higher degree of heat, and thus 

 obtained in a very concentrated ft ate. It is commonly necef- 

 fgry, however, to repeat the procefs before it can be made to 

 cryltaUize. 



Mr. Chenevix, by diftiUing the acetates, obtained a 

 pecuhar fubftance different from acetic acid, and which he 

 has denominated pyro-acetic fpirit. The acetates of potafli 

 and foda gave a greater proportion of this principle than any 

 of the metalline acetates ; but when the acetate of barytes is 

 dilUUed, the whole hquid produft confifts of this fpirit 

 without any mixture of acid whatever. No other genus of 

 falts tried, fuch as the oxalates, tartrates, or citrates, yielded 

 this fpirit, nor was acetic acid converted into it by heat. 



Pyro-acettc fpirit is a white and Umpid fluid. Its 

 tafte is at firft hot and acrid, but it becomes coohng and 

 rather urinous. Its fmell is pecuhar, and is compared by 

 Mr. Chenevix to that of a mixture of oil of peppermint and 

 bitter almonds. Its fpecific gravity is .7864. It bums 

 with a flame, white exteriorly, but of a fine blue \vithin, and 

 leaves no refidue. It boils at a temperature of 165°. It 

 mixes with water, alcohol, and volatile oils, in any proportion. 

 With hot oUve-oil it alfo mixes in any proportion ; but %vith 

 that oil cold it only mixes in certain proportions. When 

 hot it diflblves wax and tallow. It diffolves alfo a httle ful- 

 phur and phofphorus, and is an excellent folvent of camphor. 

 It diflblves potafh, and becomes dark-coloured, but it 

 may be obtained again ufialtered by diftillation. Strong 

 fulphuric acid blackens and decompofes it. Nitric acid 

 renders it yellow, and changes its properties. Muriatic 

 acid renders it brown. When diftilled with this acid 

 a combination takes place, and a fubftance is formed 

 pofTefling very different properties from muriatic ether. 

 Thefe properties are fufficient to (hew, that the pyro-acetic 

 fpirit is a diftinft fubftance, and differs entirely from 

 alcohol, ether, and volatile oils. Of courfe, therefore, as 

 Dr. Thomfon obferves, it deferves a diftinft place among 

 compound combuftibles. 



Many attempts have been made to analyfe the acetic acid. 

 Thofe moft worthy of notice are by Gay Luffac and 

 Thenard, and Berzehus. The former burnt a mixture of 

 acetate of barytes and chlorate of potafh. The refults were 

 carbonic acid and water. Berzehus's analyfis was made on 

 the fame principles, but the fait he employed was fuppofed 

 to be quite free from water. The following are the refults 

 of thefe celebrated chemifts : 



Hydrogen. 

 Gay Luffac 5-629 

 Berzelius 6.35 



+ 



Carbon. 



50.224 



46.83 



Oxygen. Acid. 



44.147 = 100 

 46.82 = 100 



If, with Dr. Thomfon, we confider the refults of Berzelius 

 moft entitled to credit, acetic acid confifts of 



3 atoms or proportions of hydrogen, weighing 0.375 



4 « of carbon 3.000 



3 ^^^—^^——— of oxygen 3.000 



Or of ten atoms or proportions, and the weight of an 

 integrant particle, will be 6-375 ; and this weight, as the tame 



A C H 



chemift has fhewn, accords very well with the conftitution of 

 the acetates. 



^CHARIA, in Botany, a genus dedicated by Profeflor 

 Thunberg, to the honour of his countryman Dr. Eric 

 Acharius, knight of the order of Wafa, a member of various 

 learned focieties, and one of the moft diftinguifhed botanifts 

 of the prefent day, particularly with regard to the Lichen 

 tnbe, which he has profoundly ftudied, and moft learnedly 

 lUuftrated. (See LiCHENES.) Dr. Acharius is now 



Regius Profeffor of Phyfic, at Vadftena, in Sweden 



Thunb. Prodr. prasf, n. 7. Willd. Sp. PI. v. 4. 327. 



Lamarck llluftr. t. 755 Clafs and order, Monoecia Trian- 



drta ; or rather, perhaps, Triandria Monozynia. Nat. Ord. 

 Eleagni, Jufl". ? 



Gen. Ch. Cal. Perianth inferior, of two fmall, ovate, 

 acute, permanent leaves. Cor. of one petal, tubular-bell- 

 fnaped, downy, in three deep, equal, elliptical fegments, per- 

 manent. Stam. Filaments three, very fhort, inferted into the 

 top of the tube of the corolla, oppofite to its fegments ; 

 anthers roundifh, of two lobes. Pijl. Germen hiperior, 

 roundilh ; ftyle folitary, thread-ftiaped, half as long as the 

 corolla ; ftigma threeK:left. Peric. Capfule ovate, of one 

 cell, and three valves. Seed fohtarj- ? globofe, rough. The 

 Jlamens are moft perfeft in the upper lowers, the pifti! in the 

 lower. 



Eif. Ch. Calyx of two leaves. Corolla of one petal, 

 three-cleft. Capfule of one cell, and three valves. Seed 

 fohtary ? 



Obf. Nothing can be more imperfeft or puzzhng than 

 the charafter and natural affinity of this genus, accorchng to 

 the materials fiimifhed by Thunberg, efpecially what regards 

 the capfule and feed. He defines the fruit, " capfule of one 

 cell, with thiee feeds." Willdenow, who feems to have had 

 no other authority than Thunberg's figure, fays, " capfule of 

 one cell and three valves, with a fohtary feed," which lail 

 account beft agrees with that figure. With refpeft to the 

 natural order of ylcharia, if we take for braSeas what Thun- 

 berg terms a calyx, the Jlotver will indicate one of Juffieu's 

 Eleagni, though the capfule of three valves is very anomalous, 

 and the lobed leaves no lefs fo. By the fpecific name 

 tragodes, or rather tragioides, and the place where the genus 

 is introduced, Thunberg appears to have confidered it as akin 

 to Tragia, (fee that article,) whach idea the afpeft of the 

 leaves, and the fomewhat va.ouocciovi% flowers, might probably 

 fuggeft. 



I. A. tragodes. Lobed Acharia. Thunb. Prodr. 14. 

 t. I. Fl. Cap. V. I. 160. Willd. n. i. — Gathered by 

 Profeffor Thunberg, near Van Stade's river, and in other 

 parts of the interior of Africa, above the Cape of Good 

 Hope, flowering in December and January. Root fibrous, 

 annual ? Stem fohtary, herbaceous, ereft ? from four to 

 twelve inches high, branched from the bottom to the top, 

 fmooth ; branches alternate, angular, ereft, fomewhat zigzag, 

 wand-hke, fubdivided. Leaves alternate, on ftalks about 

 their owti length, about an inch long, three-lobed, finely 

 downy ; lobes obovate, varioufly cut. Flowers in effeft 

 monoecious, axillary, fohtary, on fhort ftalks, reflexed, 

 fmall, the male about the upper part of the plant, female 

 lower down. The corolla is about a quarter of an inch long, 

 downy all over, as are hkewife the germen and _ftyle. Cap- 

 fule ovate-oblong, acute, thrice the length of the permanent 

 corolla. Seed nearly the fize of a pepper -com, apparently 

 black and rough. 



ACHERON, 1. I, r. Thefprotia. 



ACHILLINI, 1. 25, for 40 r. 49. 



ACHIMENES, in Botany, fo named by Browne, pof- 

 H h 2 fibJy 



