FLU 



poflible, contains no water. In this flate, its fpecific gravity 

 is 1 .0609. AYlien united to a certain portion of water, 

 its fpecific gravity becomes as high as 1.250. When a drop 

 is let fall into water, a hiffing noife is heard, fimilar to that 

 occailoned by a hot iron. When a few drops of water are 

 let fall into fluoric acid, it enters into ebullition. A large 

 proportion of water may be added-without deitroying its 

 fuming property. Care mull be taken not to breathe the 

 fumes of this acid, as they are very deleterious. When a 

 drop of it falls upon the Jkin, it afts as a powerful corrofive, 

 and occafions a fore which does not foon heal. 



Refpefting the nature of this acid, the opinion of the 

 older chemifts, and even of Gay Luflac and Thenard, was, 

 that it is compofed of an unknown bafis and oxygen. 

 M. Ampere, however, ftarted the notion that it is analogous 

 to muriatic acid, or a compound of hydrogen, and a fup- 

 porter of combuftion, to which the name oijliwrine has been 

 given ; and this opinion has been fince fupported by Sir H. 

 Davy, and though its truth has not been abfolutely demon- 

 ftrated, yet upon the whole perhaps it is the moft probable. 

 On this fuppofition, fluoric acid is a compound of one atom 

 fluorine, and one atom hydrogen. See Simple Bodies. 

 Fluoric acid combines with all the bafes iormwgJJuates. 



Filiate of Ammonia This fait may be formed by faturat- 



ing pure fluoric, acid with ammonia. It is neutral when firft 

 formed, but becomes acid when evaporated. It does not 

 cryfl:allize, but when heated, flies off in thick white vapours. 

 Filiate of Potajli. — This fait maybe formed in the' fame 

 manner as the lafl. It has a very fharp tafl;e, cryftallizes 

 with difiiculty, is very deliquefcent, and of courfe foluble in 

 vi'ater. When heated, it undergoes firft the aqueous, and 

 afterwards the igneous fufion. Sulphuric acid decompofes 

 it, driving off" fluoric acid in vapour. 



Fluate of Soda. — This fait may be formed as above. It 

 has much lefs tafte than fluate of potafli. It is not altered 

 by expofure to the air, and is rather more foluble in hot than 

 in cold water. On cooling, therefore, it feparates in fmall 

 cryftals, or more frequently in the form of a folid and tranf- 

 parent cruft on the furface of the water. 



Fluate of Lime. — This fait exifts abundantly native. It 

 is called Fluor spar (which fee), and is the fubft;ance from 

 which this acid is always obtained. It is compofed, accord- 

 ing to Davy's analyfis, of 



Fluorine - 20. - 100. 



Calcium - 26.25 " - I3I-25 



Fluate of Barytes. — This fait is taftelefs, infoluble in 

 water, but foluble in excefs of fluoric acid, and likewife in 

 nitric and muriatic acid. It is compofed of 

 Fluorine - 20. 



Barium - 87.5 



Fluate of Stront'tan. — This fait 

 perties as fluate of barytes. 



Fluate of Magnefia. — This is a 

 ble in water, and fcarcely foluble in acids 



Fluate of Yttr'ia, Fluate of Alumina, and Fluate of Zirconla, 

 are likewife white infoluble powders. The 



Fluate of Glucina is foluble in hot water, and precipitates 

 in fmall cryftals as the water cools. 



It is extremely probable, as Dr. Thomfon remarks, that 

 the above falts are in reality fluorides, or compounds of 

 fluorine, with the metallic bafes of the earths. 



The metalhc fluates are not upon the whole an interefting 

 clafs of bodies. The fluates of iron, manganefe, zinc, and tin, 

 are white infoluble powders. The fluate of col/alt is of a red 

 colour. The fluate of lead exifts in the form of brilliant 

 plates. The fluate of copper, of fmall blue-coloured foluble 



F O L 



cryftals. The Jiiate of mercury of fmall lamellar yellow 

 cryftals. The fluate offilver is very foluble in water, and 

 does not cryftallize. It cannot be formed by the diredl 

 union of fluoric acid and fdver, but it is formed when fluate 

 of mercury is made to aft upon filver. 



Fluoboric Acid. — Fluorine has the property of combining 

 with boron, and forming an acid which has received the 

 above appellation. It may be formed by mixing together 

 in a retort one part of finely pounded fufed boracic acid, and 

 two parts of fluor fpar in powder, and twelve parts of ful- 

 phuric acid. The heat of a lamp is then to be appHed, and 

 the acid comes over in the form of a gas, which muft be 

 received over mercury. For this procefs we are indebted 

 to Dr. John Davy, but the acid itfelf was firft difcovered 

 by Gay Lufl'ac and Thenard in 1808. 



Fluoboric acid thus obtained is colourlefs, and poflefles 

 the mechanical properties of common air. Its fmell is fimi- 

 lar to that of muriatic acid, and its tafte is exceedingly acid. 

 It inftantly gives a red colour to vegetable blues. Its fpecific 

 gravity, as determined by Dr. Davy, is 2.3709. Water 

 abforbs about 700 times its bulk of this gas, and becomes 

 flightly vifcid, hke fulphuric acid, and like it requires a high 

 temperature to make it boil. It alfo charrs animal and vege- 

 table fubftances, and is capable of forming an ether when 

 diftilled with alcohol. It combines with the different bafes, 

 and forms a clafs of falts called fluoborates, which have been 

 little examined. On the fuppofition that it is a compound 

 oi fluorine and boron, which feems to be the moft probable 

 opinion, its corapofition will be 



100. 



437-5 

 poffefles the fame pro- 



taftelefs powder, infolu- 



Fluorine 

 Boron 



20. 

 8.75 



100. 

 43-75 



228.57 



100. 



Fluofilicic Acid. — Fluorine has alfo the property of com- 

 bining w\thfiUcon, and forming a powerful acid. Tliis com- 

 pound was firft difcovered by Scheele, but it is to Dr. J. 

 Davy that we are principally indebted for the correct account 

 of its properties. It may be formed by putting a mixture 

 of equal parts of pounded fluor fpar and glafs into a retort, 

 and pouring over the mixture fulphuric acid fufiicient to con- 

 vert the whole into a pafte. Heat is then to be applied, and 

 the acid fpeedily comes over in the form of a gas, and may- 

 be collefted over mercury. Fluofihcic acid gas is colour- 

 lefs, and pofteftes the mechanical properties of common air. 

 Its fmell refembles that of muriatic acid. It fmokes when 

 allowed to efcape into the atmofphere. It inftantly reddens 

 vegetable blues. Its fpecific gi-avity, according to Dr. 

 Davy, is 3.5735- Water abforbs about 263 times its bulk 

 of it, but at the fame time it is partly decompofed, and filica 

 is depofited. When pafled through liquid ammonia, the 

 whole of the filicon is depofited in the form of fihca : this 

 enabled Dr. Davy to effeft its analyfis, the refult of which 

 appears to ftiew that it is a compound of one atom filicon 

 and one atom fluorine. 



The fluifilicates have not been much examined. The 

 JluoJiUcate of lime exifts abundantly native, and has not hither- 

 to been diftinguiftied from fluor fpar. It may, however, be 

 eafily recogniled by heating it in metallic veflels with ful- 

 phuric acid, when it yields fluofihcic acid gas, while fluor 

 fpar does not. 



FLUORINE. See Fluoric Acid. 



FLUOSILICIC Acid, Fluosilicates. See Fluoric 

 Acid. 



FLUTE Traversiere. See Traversiere. 



FLUVANNA, 1. 5, /-. 4775- of whom 2142 are flaves. 



FOAL-Birth. See Age of the Horfe, and Horse. 



FOLKINGHAM, or Falkixgham, 1. 5 and 6, r. 106 



houfes, and 659 inhabitants. ,,„r^^xTT- 



^^ 3 Q 2 FOLKSTONE, 



