VOL 



553. Some authors fay that for a certain tune the Lom- 

 bards fixed their court there. 



VOLATERRANA Vada, a town or borough of 

 Italy, in Etruria, with a port at the mouth of the Cecinna, 

 according to Pliny. It is now called Vadi. 



VOLATICA, in Medicine, 3. name given by authors to 

 a fort of wandering pain, attended with a tumour, and 

 afFefting, at different times, different parts of the body. It 

 is by fome accounted a fpecies of the fcurvy ; by others, of 

 the leprofy. 



VOLATILE, in Phyfia, is commonly ufed to denote 

 a mixt body, whofe integral parts are eafily diffipated by 

 fire or heat ; but it is more properly ufed for bodies whofe 

 elements, or firll component parts, are eafily feparated from 

 each other, and difperfed in air. 



As thofe bodies which by heat fuffer no diminution of 

 their weight are faid to be fixed, fo thofe which do lofe of 

 their weight are faid to be volatile ; and they are faid to be 

 more or lefs volatile, according as a greater or lefs degree 

 of heat is reqiiifite for producing a feparation of their 

 parts. Perhaps, indeed, every body is, rigoroufly fpeaking, 

 volatile : but as there are fome, the volatihty of which can 

 be only rendered fcnfible by the a&ion of a fire much more 

 violent than any which we can produce, we confider thefe 

 bodies as being fixed, or not volatile. 



Minerals, for the generality, are lefs volatile than vege- 

 tables ; and vegetables are lefs fo than animals. 



The chemills diftinguifh between volatile falts and fixt 

 falts. The capitals of aludels flop and coUeft the volatile 

 parts of fubftances, in fublimation, and make what we call 

 P.oivers. 



" The particles of fluids which do not cohere very ftrongly 

 together, and are of fuch fmallnefs as renders them moll 

 fuiceptible of thofe agitations which keep liquors in a fluor, 

 are eafily rarefied into vapour ; and, in the language of the 

 chemills, are volatile. Thofe which are groffer, and by 

 that means lefs fufceptible of alterations, or vfhich cohere 

 by a ftronger lieat, or, perhaps, not without fermentation ; 

 thefe are what the chemills call fixt bodies." Newton's 

 Optics, p. S71. 



Volatile yilia/i. See Alkali. 



Volatile Salt of Amber. See Amber. 



Volatile Oil, in Rur^l Economy, is that fort which has 

 a fragrant aromatic fmell, and which is fometimes called 

 ejfential oil. It is ftated by fir Humphrey Davy to differ 

 from fixed oil, in being capable of evaporation by a much 

 lower degree of heat, in being foluble in alcohol, and in 

 poffefling a very flight degree of folubility in water. There 

 is a great number of this fort of oils, diftingui(hed by 

 their fmell, their tafte, their fpecific gravity, and other fen- 

 fible qualities. A ftrong and peculiar odour may, however, 

 be confidered as the great charafteriftic of each fort ; the 

 volatile oils inflame with more facility than the fixed oils, and 

 afford by their combullion different proportions of the fame 

 fubftances, water, carbonic acid, and carbon. 



It is faid that the peculiar odours of plants feem, in almoft 

 all cafes, to depend upon the peculiar oils of this fort they 

 contain. All the perfumed dillilled waters owe their pecu- 

 liar properties to the volatile oils they hold in folution. By 

 collefting the aromatic oils, the fragrance of flowers, fo 

 fugitive in the common courfe of nature, is as it were em- 

 bodied and made permanent. It cannot be doubted, it is 

 faid, that the volatile oils conCfl of carbon, hydrogen, and 

 oxygen ; but no accurate experiments have as yet been made 

 on the proportions in which thefe elements are combined. 

 As the fragrance of flowers depends upon the volatile oils 

 they contain ; and thefe oils, by their conflant evaporation, 



VOL 



furround the flower with a kind of odorous atmofphere ; 

 which, at the fame time that it entices larger infetls, may 

 probably preferve the parts of fructification from the ravages 

 of fmaller ones ; volatile oils, or odorous fubftances, feem. 

 it is faid, particularly deltriiftive to thefe minute infeits 

 and animalcules which feed on the fubftance of vegetables : 

 thoufands of aphides may be ufually feen in the ilalk and 

 leaves of the rofe ; but none of them are ever obferved on 

 the flower. Camphor is the fubftance ufed to preferve the 

 colleftions of naturalifts. The woods that contain aromatic 

 oils are remarkable for their indeftriidlibility, and for their 

 exemption from the attacks of infedts : this is particularly 

 the cafe with the cedar, rofe-wood, and cyprefs. The 

 gates of Conftantinople, which were made of this laft fort 

 of wood, ftood entire, it is faid, from the time of Conftan- 

 tine, their founder, to that of pope Eugene IV., a period 

 of 1 100 years. 



This fort of oils is afforded by diftillation, coming over 

 with the water, and floating on the top of it in fmall glo- 

 bules. It is coUefted by pouring a quantity of the diftillcd 

 water with the oil, as it comes over into a velTel, fo con- 

 ftrufted as to fuffer the watery part to efcape by a ftop- 

 cock near the bottom ; the veffel or apparatus is again filled,, 

 and when fettled, the water is again let out ; in this manner 

 the oil is oollefled in great quantities, floating as above. 

 This effential or etherial oil refides, it is fuppofed by fome, 

 in a particular part of the plant, but which is different in 

 different forts. And it is faid that the oils vary in their 

 nature or properties in different forts of plants. 



It is noticed by the above writer, that the volatile oils have 

 never been ufed as articles of food ; many of them are em- 

 ployed in the arts, in the manufadlure of pigments and var- 

 mlhes ; but that their moft extenfive application is as per- 

 fumes in the hands of the perfumer, and manufafturer in that 

 way. On the contrary, the fixed oils are very nutritive fub- 

 ftances, and are of great importance in their applications to 

 the purpofes of life. See Oil. 



Volatile, Sal Ohojum. See Sal. 



Volatile Salt. See Salt. 



VOLATILISATION, or Volatilization, the ad 

 of rendering fixt bodies volatile, or refolving them, by fire, 

 into a fine, fubtle vapour, or fpirit, which eafily diffipates, 

 and flies away. 



All bodies, even the moft fixt, as gold, may be volati- 

 lized, either of themfelves, or with the admixture of fome 

 volatile fubftance, or fpirit ; by diftillation, or fubhmation. 



In the Memoiis of the Royal Academy we have a dif- 

 couife on the volatihzation of the fixed falts of plants, by 

 M. Romberg. 



VOLATILITY, in Chemijlry, is a property that many 

 bodies have of being reduced into light vapours, which ex- 

 hale when they are expofed to the adlion of fire. This qua- 

 lity is oppofed to fixity, and is owint^ to the greater or lefs 

 dilatability which bodies have, when expofed to fire. See 

 Volatile, Sublimation", Sec. 



VOLCjE Arecomici, in Ancient Geography, contradif- 

 tiiiguifhed from the Te8ofages, were a branch of a people, 

 who occupied, in the Narbonnefe province, the whole fpace 

 that lies between the Rhone and the Garonne. The Are- 

 comici were fituated near the Rhone, and extended along 

 the fea in that territory which is now called Lower Lan- 

 guedoc. When Hannibal traverfed the fouthern part of 

 Gaul, in his way to Italy, the Arecomici were not bounded 

 by the Rhone, but pofFefTed territory on both fides of the 

 river. The chain of Mons Aberna feparated the Areco- 

 mici from the Ruteni and the Gabati. But their limits with 

 regard to the Teftofages ai'e not eafily afcertained. Ac- 

 cording 



