490 FUCUS 



To obtain the dyo in a state of greater purity it is converted into a lime or 

 alumina lake. For this purpose tlio ammoniacal solution is precipitated with 

 chloride of calcium or with alum; the red colouring matter then remains almost 

 wholly in solution, and the lakes are collected, carefully washed with cold water, 

 and dried at a gentle heat. They then present a violet or bluish aspect, and acquire 

 a coppery lustre by friction. 



French purple is generally sent into the market in the form of lime lake. To 

 render it available for dyeing, the lake is decomposed arid the colouring matter set 

 free. For this purpose the lake is reduced to an impalpable powder, which is 

 boiled with oxalic acid to separate the lime, and the colouring matter then dissolved 

 out by ammonia. The lake may also bo directly decomposed by boiling it with 

 carbonate of ammonia. For printing, tho lake is dissolved in acetic acid, and the 

 solution mixed with alcohol and thickened. 



In this manner, very fine and pure mauve and dahlia tints are obtained, especially 

 on silk, without tho use of mordants, properly so called. French purple, moreover, 

 mixes easily with other colouring matters, such as ultramarine, indigo, carmine, 

 cochineal, aniline red, &c., producing the most varied and delicate tints. 



Recently, however, the manufacture of French purple has diminished in im- 

 portance by the competition of tho coal-tar purple. The upshot of this struggle 

 will depend on the relative beauty and purity of the tints obtained, and on their 

 comparative cost : for, so far as regards fastness and resistance to tho influence 

 of light, French purple is superior to aniline purple. See Watte's ' Dictionary of 

 Chemistry.' 



FRENCH TUB. A dyer's term for a mixture of protochloride of tin and logwood, 

 called also ' plum tub.' 



FRICTION. The resistance to motion which depends on the structure of the 

 surfaces in contact. Friction is usually divided into two kinds : sliding friction and 

 rolling friction. The questions involved in the consideration of friction are purely 

 engineering, and cannot therefore be treated here. One very important element may, 

 however, be named, as showing the importance of exact science in connection with 

 the improvements in mechanics. By friction heat is evolved. It is found by accurate 

 experiment, that the quantity of Jicat evolved is exactly sufficient to reproduce the effort 

 caused in overcoming the friction. Joule and Thomson. 



FRIEZE. (Frise, Fr. ; Frisa, Sp.) The nap on woollen cloth ; hence it is applied 

 to a coarse kind of woollen cloth or stuff with a nap on one side. See BAIZE. 



FRIT. See ENAMEL and GLASS. 



FRITTING-. It was formerly the practice in glass-making to heat tho glass- 

 mixture to such an extent that an incipient fusion, or caking-togethcr, commenced, 

 during which the silica began to act upon the bases, the carbonic acid was partially 

 expelled, and a frit was produced. The Schmelz of the Austrian and Bohemian 

 glass-houses is a true frit, or an imperfectly-melted mixture, composed of lixiuatcd 

 ashes and sand. See GLASS. 



FRUIT. Tho fruit of a plant consists essentially of tho matured ovary enclosing 

 the seeds, or ripened ovules. But in many cases other parts of tho flower enter into 

 the composition of the fruit ; in the apple, for example, the calyx adheres to tho ovary, 

 and, becoming succulent, forms the greater portion of the fruit. Few vegetable 

 structures are more liable to be misunderstood than the fruit ; many parts of a plant 

 being popularly called fruit which have no scientific claim to the name, whilst many 

 structures which are truly fruit in botanical language would not bo generally recog- 

 nised as such. The common idea of a soft succulent structure, like the berry and tho 

 drupe, is by no means necessary to tho constitution of a fruit, many kinds of fruit, 

 such as the nut and the capsule being dry and more or less hard. Among umbelli- 

 ferous plants, tho structures commonly called ' seeds,' such as aniseed, caraway seeds, 

 coriander seed, &c., are true fruits ; the external envelope, or seed-vessel, being firmly 

 adherent to tho enclosed seed. So too tho grains of cereals are fruits, tho albuminous 

 seed being closely invested in a thin membranous coat, or pericarp. 



Fruits not only furnish articles of diet in some cases of groat importance, as tho 

 date and the bread-fruit but somo of them yield oil olive-oil and palm-oil, for 

 example whilst others possess a strong integument from which useful vessels aro pro- 

 pared, such as tho gourds and calabashes. 



FUCHSINE. Sco ANILINK RED. 



FTTCHSITE, A green micaceous mineral, containing chromium, found in tho 

 Tyrol. 



FUCUS. A genus of sea-weeds. In the Fucus scrratus and F. ccramoidcs silver has 

 been detected : Malaguto has stated to the extent of -n^noo' * n ^10 ashes of these plants. 

 It has also been stated that these and somo other plants contain lead and copper. 



