FL.UELEN 



3217 



FLUORINE 



Fliielen. Village of Switzerland, 

 in the canton of Uri. It stands at 

 the head of Lake Uri, a S.E. exten- 

 sion of Lake Lucerne, 2 m. N.N. W. 

 of Altdorf on the St. Gothard Rly. 

 The port for Altdorf, it is the ter- 

 minus for lake steamers. The 

 Axenstrasse carriage road, con- 

 structed in 1863-65, leads from 

 here to Brunnen. The village has 

 a chateau and several hotels. 

 Pop. 1,010. 



Fluellen. Character in Shake- 

 speare's Henry V, a Welsh officer 

 in the king's army. Of hasty tem- 

 per and verbose speech, he is ever 

 ready to compare the fighting of 

 his day with that of the ancients. 



Flugel Horn. Brass instru- 

 ment. It is similar to the cornet, 

 but of wider bore, like the bugle, 

 and of mellow, horn-like tone. It 

 is a modern improvement of the 

 key bugle. The soprano instru- 

 ment is the most usual. The term 

 means wing horn. See Cornet. 



Fluid. That form of matter 

 which is unable to resist perman- 

 ently any shear stress, however 

 small. Matter is solid, liquid or 

 gaseous. Fluids are liquids or gases 

 and they are distinguished from 

 solids in that they owe their shape 

 at any particular time to a con- 

 taining vessel or restraining forces. 

 The line of demarcation between a 

 solid and a liquid is one which can- 

 not easily be drawn. Many solids 

 flow like liquids, e.g. a glacier down 

 a mountain side, though at a con- 

 siderably slower rate, while even 

 solids like lead can be made to flow 

 under the action of suitable forces. 

 See Flow; Hydrodynamics; Hydro- 

 statics; Gas; Liquid. 



Fluid Measures. Nearly all 

 fluid measures have been derived 

 from corresponding measures of 

 length or weight and suffer all the 

 variations of the latter which were 

 taken from parts of the human 

 body. It is only within compara- 

 tively recent times that fluid meas- 

 ures have become standardised by 

 law in different countries. In the 

 United Kingdom the gallon is the 

 unit measure for fluids, and in 

 countries where the metric system 

 is standardised the litre is the 

 unit. A gallon contains a little 

 over four and a half litres. See 

 Weights and Measures. 



Fluke. Group of trematode 

 worms of parasitic nature, usually 

 leaf-shaped. One, the liver fluke 

 (Fasciola hepatica), in its adult 

 condition lives in and devours the 

 liver of the sheep, causing the 

 much-dreaded "rot." The eggs 

 pass out of the body of the sheep 

 with the dung, and if they fall in a 

 wet place hatch out into tiny 

 ciliated embryos that swim about 

 in search of a small water snail 



(Limnaea truncatula), perishing in 

 about eight hours if unsuccessful. 

 Within the body of such a snail 

 other stages of life are passed, un- 

 til finally one shaped like a minute 

 tadpole is attained (cercaria). This 

 leaves the snail and swims to a 

 stem or leaf of grass, to which it 

 attaches itself, and passes into an 

 encysted or dormant stage. Its tail 

 has gone, it is covered by a limy 

 coat, and resembles the adult fluke 

 except in size. 



Should a sheep swallow one of 

 these capsules or cysts, the limy 

 covering is dissolved by the gastric 

 juice, and when it passes into the 

 small intestine the tiny fluke 

 makes its way up the bile-duct into 

 the liver of its victim, there to in- 

 crease in size and become sexually 

 mature. The disease may be en- 

 tirelv prevented by keeping sheep 



Flugel Horn. Improved model of 

 B flat horn 



' By courtesy of Satakes & Son 



away from damp, ill-drained land. 

 As there is no cure for the disease, 

 sheep showing signs of rot should 

 be slaughtered as soon as possible. 

 See Sheep. 



FluorantheneoR IDRYL(C 15 H 1Q ). 

 Substance found in coal-tar and in 

 the residue known as " stuppfett " 

 obtained after the distillation of 

 mercury ores. Crude pyrene from 

 coal -tar is converted into the 

 picric acid compound, whence the 

 fluoranthene is obtained in the 

 free state and recrystallised. 



Fluorescence. Absorption of 

 light of certain colour or wave- 

 length, and radiation or emission 

 of light of other wave-lengths by 

 certain bodies. A solution of the 

 green colouring matter of plants, 

 chlorophyll, placed in a dark room 

 where a beam of white light reaches 

 it, becomes luminous and emits a 

 red light from the portions of the 

 liquid on which the white light 

 falls. Paraffin oil, solutions of 

 quinine, of some of the coal-tar 

 dyes such as the red-ink cosine, 

 and of salts, such as barium or 

 potassium plat ino -cyanide, act 

 similarly. Beams of coloured light 

 do not always excite fluorescence. 



For example, although red, 

 yellow or green fail, blue or violet 

 light will at once provoke in a 

 solution of quinine the character- 

 istic pale blue fluorescence. The 

 solution of chlorophyll, on the 

 other hand, retains its red fluores- 

 cent light when exposed to most 



kinds of light, though in violet 

 light the glow becomes brownish. 

 The light emitted by a fluorescent 

 body is found spectroscopically not 

 to be light of one colour or of one 

 wave-length only, but to comprise 

 light of various colours, with a 

 wave-length always greater than 

 the wave-length of the light which 

 causes the fluorescence. Thus when 

 a beam of sunlight passes through 

 a solution of quinine, it is deprived 

 of its invisible ultra-violet rays, 

 which the quinine converts into 

 blue and violet rays of longer wave 

 length, visible to the eye. 



The emission of the fluorescence 

 stops as soon as the light which 

 causes it is cut off. But some sub- 

 stances, particularly the sulphides 

 of barium, calcium and strontium, 

 continue to emit light after the 

 exciting cause has been cut off. 

 Thus, after exposure, they glow in 

 the dark. This glow is called phos- 

 phorescence, although the glow of 

 phosphorus itself is not due to 

 these causes, but to slow chemical 

 action. See Phosphorescence. 



Fluorescein. An aniline dye 

 formed by heating five parts of 

 phthalic anhydride with seven 

 parts of resorcin at a temperature 

 of 200 C. in an enamelled cast-iron 

 pot. When the' reaction has taken 

 place the mass becomes solid and 

 forms a dark-brown cake. The 

 solution in alcohol or alkalies 

 exhibits a brilliant yellow -green 

 fluorescence from which the sub- 

 stance takes its name. It is used for 

 dyeing silk and also for preparing 

 the liquid in druggists' show bottles. 



Fluorine. Gaseous element of 

 greenish-yellow colour, first isolated 

 by Moissan in 1886. Its chemical 

 symbol is F. Derbyshire-spar or 

 " blue- John " is calcium fluoride. 

 Cryolite, a double fluoride of alu- 

 minium and sodium, is found in 

 Greenland, and the element occurs 

 widely throughout the mineral 

 kingdom, but only in small amounts. 

 Scheele in 1771 first recognized that 

 fluorspar is a fluoride of calcium 

 and prepared hydrofluoric acid, but 

 all attempts to prepare fluorine were 

 unsuccessful before 1886. It was 

 liquefied in 1897 and solidified 

 in 1903. 



The difficulties in preparing 

 fluorine are very great on account 

 of the extremely active chemical 

 affinity it has for glass and most 

 metals. Traces of the gas are very 

 irritating to the mucous membrane, 

 and if brought into contact with 

 the skin the gas causes a bad burn. 

 Alcohol, ether, benzene and tur- 

 pentine take fire on contact with 

 fluorine. Moissan isolated the 

 element by the electrolysis of 

 anhydrous hydrofluoric acid to 

 which acid potassium fluoride had 



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