See also:

• FILTER (a word common in various forms to most European languages, adapted from the medieval Lat. fi-ltrum, felt, a material used as a filtering agent)

FILTER (a word See also:

• COMMON

common in various forms to most See also:

• EUROPEAN

European See also:

• LANGUAGES

languages, adapted from the See also:

• MEDIEVAL

medieval See also:

• LAT

Lat. fi-ltrum, See also:

• FELT (cognate with Ger. Filz, Du. vilt, Swed. and Dan. fill; the root is unknown; the word has given Med. Lat. filtrum, " filter ")

felt, a material used as a filtering See also:

• AGENT (from Lat. agere, to act)

agent)  , an arrangement for separating solid See also:

• MATTER

matter from liquids . In some cases the operation of filtration is performed for the See also:

• SAKE

sake of removing impurities from the filtrate or liquid filtered, as in the See also:

• PURIFICATION

purification of See also:

• WATER

water for drinking purposes; in others the aim is to recover and collect the solid matter, as when the chemist filters off a precipitate from the liquid in which it is suspended . In regard to the purification of water, filtration was See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

long looked upon as merely a See also:

• MECHANICAL

mechanical See also:

• PROCESS

process of straining out the solid particles, whereby a turbid water could be rendered clear . In the course of See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

time it was noticed that certain materials, such as See also:

• CHARCOAL

charcoal, had the See also:

• POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

power to some extent also of softening hard water and of removing organic matter, and at the beginning of the loth See also:

• CENTURY (from Lat. centuria, a division of a hundred men)

century charcoal, both See also:

• ANIMAL
• ANIMAL (Lat. animalis, from anima, breath, soul)

animal and See also:

• VEGETABLE

vegetable, came into use for filtering purposes . Porous See also:

• CARBON (symbol C, atomic weight 12)

carbon blocks, made by strongly See also:

• HEATING

heating a mixture of powdered charcoal with oil, See also:

• RESIN (through O.Fr. resine, modern reline, from Lat. resina, prcbably Latinized from Greek Pirivrt, resin)

resin, &c., were introduced about a See also:

• GENERATION (from Lat. generare, to beget, procreate; genus, stock, race)

generation later, and subsequently various preparations of See also:

• IRON [symbol Fe, atomic weight 55.85 (0=16)]

iron (spongy iron, magnetic See also:

• OXIDE

oxide) found favour . Innumerable forms of filters made with these and other materials were put on the See also:

• MARKET (Lat. mercatus, trade or place of trade)

market, and were extolled as removing impurities of every See also:

• KIND (O. E. ge-cynde, from the same root as is seen in " kin," supra)

kind from water, and as affording See also:

• COMPLETE

complete See also:

• PROTECTION

protection against the communication of disease . But whatever merits they had as clarifiers of turbid water, the See also:

• ADVENT (Lat. Adventus, sc. Redemptoris, " the coming of the Saviour ")

advent of See also:

• BACTERIOLOGY

bacteriology, and the recognition of the fact that the bacteria of certain diseases may be water-See also:

• BORNE, KARL LUDWIG (1786–1837)

borne, introduced a new criterion of effectiveness, and it was perceived that the removal of solid particles, or even of organic impurities (which were realized to be important not so much because they are dangerous to See also:

• HEALTH

health per se as because their presence affords grounds for suspecting that the water in which they occur has been exposed to circumstances permitting contamination with infective disease), was not sufficient; the See also:

• FILTER (a word common in various forms to most European languages, adapted from the medieval Lat. fi-ltrum, felt, a material used as a filtering agent)

filter must also prevent the passage of pathogenic organisms, and so render the water sterile bacteriologically . Examined from this point of view the See also:

• MAJORITY (Fr. majorite; Med. Lat. majoritas; Lat. major, greater)

majority of domestic filters were found to be gravely defective, and even to be worse than useless, since unless they were frequently and thoroughly cleansed, they were liable to become favourable breeding-places for microbes . The first filter which was more or less completely impermeable to bacteria was the See also:

• PASTEUR, LOUIS (1822-1895)

Pasteur-Chamberland, which was devised in Pasteur's laboratory, and is made of dense See also:

• BISCUIT (pronounced according to the old spelling " bisket," a Fr. form from Lat. bis, twice, and coctum, cooked, in reference to the original method of preparation; cf. Ital. biscotto, Sp. bizcocho, &c.)

biscuit See also:

• PORCELAIN

porcelain . The filtering See also:

• MEDIUM

medium in this, as in other filters of the same kind, takes the See also:

• FORM (Lat. forma)

form of a hollow See also:

• CYLINDER (Gr. KvAwSpos, from KvXivaety, to roll)

cylinder or " See also:

• CANDLE (Lat. candela, from candere, to glow)

candle," through the walls of which the water has to pass from the outside to the inside, the candles often being arranged so that they may be directly attached to a tap, whereby the See also:

• RATE

rate of flow, which is See also:

• APT

apt to be slow, is accelerated by the pressure of the See also:

• MAIN (from the Aryan root which appears in " may " and " might," and Lat. magnus, great)
• MAIN (Lat. Moenus)

main . But even filters of this type, if they are to be fully relied upon, must be frequently cleaned and sterilized, and See also:

• GREAT

great care must be taken that the See also:

• JOINTS

joints and connexions are watertight, and that the candles are without cracks or flaws . In cases where the water See also:

• SUPPLY (through Fr. from Lat. supplere, to fill up)

supply is known to be infected, or even where it is merely doubtful, it is See also:

• WISE, HENRY ALEXANDER (1806-1876)
• WISE, ISAAC MAYER (1819-1900)

wise to have recourse to sterilization by boiling, rather than See also:

• TRUST

trust to any filter .

Various See also:

• MACHINES

machines have been constructed to perform this operation, some of them speciallydesigned for the use of troops in the See also:

• FIELD (a word common to many West German languages, cf. Ger. Feld, Dutch veld, possibly cognate with O.E. f olde, the earth, and ultimately with root of the Gr. irAaror, broad)
• FIELD, CYRUS WEST (1819-1892)
• FIELD, DAVID DUDLEY (18o5-1894)
• FIELD, EUGENE (1850-1895)
• FIELD, FREDERICK (18o1—1885)
• FIELD, HENRY MARTYN (1822-1907)
• FIELD, JOHN (1782—1837)
• FIELD, MARSHALL (183 1906)
• FIELD, NATHAN (1587—1633)
• FIELD, STEPHEN JOHNSON (1816-1899)
• FIELD, WILLIAM VENTRIS FIELD, BARON (1813-1907)

field; those in which See also:

• ECONOMY

economy of See also:

• FUEL (O. Fr. feuaile, popular Lat. focalia, from focus, hearth, fire)

fuel is studied have an See also:

• EXCHANGE

exchange-heater, by means of which the incoming See also:

• COLD (in O. Eng. cald and ceald, a word coming ultimately from a root cognate with the Lat. gelu, gelidus, and common in the Teutonic languages, which usually have two distinct forms for the substantive and the adjective, cf. Ger. Kolte, kalt, Dutch koude

cold water receives See also:

• HEAT (0. E. haktu, which like " hot," Old Eng. hat, is from the Teutonic type haita, hit, to be hot; cf. Ger. hitze, heiss; Dutch, hitte, heet, &c.)

heat from the outgoing hot water, which thus arrives at the point of outflow at a temperature nearly as See also:

• LOW, SETH (1850- )
• LOW, WILL HICOK (1853- )

low as that of the supply . Chemical methods of sterilization have also been suggested, depending on the use of See also:

• IODINE (symbol I, atomic weight '26.92)

iodine, See also:

• CHLORINE (symbol Cl, atomic weight 35`46 (0=16)

chlorine, See also:

• BROMINE (symbol Br, atomic weight 79-96)

bromine, See also:

• OZONE

ozone, See also:

• POTASSIUM [symbol K (from kalium), atomic weight 39.114 0=16)]

potassium permanganate, See also:

• COPPER (symbol Cu, atomic weight 63.1, H=1, or 63.6, O = 16)

copper sulphate or chloride and other substances . For the See also:

• SAND
• SAND, GEORGE (1804-1876)

sand-filtration of water on a large See also:

• SCALE
• SCALE (1) A

scale, in which the presence of a See also:

• SURFACE

surface film containing zooglaea of bacteria is an essential feature, see WATER SUPPLY . Filtration in the chemical laboratory is commonly effected by the aid of a See also:

• SPECIAL

special kind of unsized See also:

• PAPER
• PAPER (Fr. papier, from Lat. papyrus)

paper, which in the more expensive varieties is practically pure See also:

• CELLULOSE

cellulose, impurities like feric oxide, alumina, See also:

• LIME
• LIME (O. Eng. lim, Lat. limes, mud, from linere, to smear)

lime, See also:

• MAGNESIA

magnesia and See also:

• SILICA

silica having been re-moved by treatment with hydrochloric and hydrofluoric acids . A circular piece of this paper is folded twice upon itself so as to form a quadrant, one of the folds is pulled out, and the See also:

• CONE (Gr. Kwvos)

cone thus obtained is supported in a See also:

• GLASS
• GLASS (O.E. glees, cf. Ger. Glas, perhaps derived from an old Teutonic root gla-, a variant of glo-, having the general sense of shining, cf. " glare," " glow ")
• GLASS, STAINED

glass or porcelain See also:

• FUNNEL (through an O. Fr. founil, found in Breton, from Lat. infundibulum, that through which anything is poured, from fundere, to pour)

funnel having an apical See also:

• ANGLE (from the Lat. angulus, a corner, a diminutive, of which the primitive form, angus, does not occur in Latin; cognate are the Lat. angere, to compress into a bend or to strangle, and the Gr. ayKOS, a bend; both connected with the Aryan root ank-, to

angle of 6o° . The liquid to be filtered is poured into the cone, preferably down a glass See also:

• ROD (O.E. rodd, probably related to Norw. rudda, stick, rodda, stake)
• ROD, EDOUARD (1857-1910)

rod upon the sides of the funnel to prevent splashing and to preserve the See also:

• APEX

apex of the filter-paper, and passes through the paper, upon which the solid matter is retained . In the See also:

• CASE
• CASE, JOHN (d. 1600)

case of liquids containing strong acids or alkalis, which the paper cannot withstand, a plug of carefully purified See also:

• ASBESTOS

asbestos or glass-See also:

• WOOL, WORSTED AND WOOLLEN MANUFACTURES

wool (spun glass) is often employed, contained in a bulb blown as an enlargement on a narrow " filter-See also:

• TUBE (Lat. tuba)

tube." To accelerate the rate of filtration various devices are resorted to, such as lengthening the tube below the filtering material, increasing the pressure on the liquid being filtered, or decreasing it in the See also:

• RECEIVER

receiver of the filtrate . R . W . See also:

• BUNSEN, CHRISTIAN CHARLES JOSIAS, BARON VON (1791-186o,)
• BUNSEN, ROBERT WILHELM VON (1811-1899)

Bunsen may be regarded as the originator of the second method, and it was he who devised the small cone of See also:

• PLATINUM [symbol Pt, atomic weight 145.0 (0=16)]

platinum See also:

• FOIL

foil, sometimes replaced by a cone of See also:

• PARCHMENT

parchment perforated with pinholes, arranged at the apex of the funnel to serve as a support for the paper, which is apt to burst under the pressure See also:

• DIFFERENCES, CALCULUS OF (Theory of Finite Differences)

differences . In the so-called " See also:

• BUCHNER, FRIEDRICH KARL CHRISTIAN LUDWIG (1824-1899)

Buchner funnel," the filtering See also:

• VESSEL (O. Fr. vaissel, from a rare Lat. vascellum, dim. of vas, vase, urn)

vessel is cylindrical, and the paper receives support by being laid upon its See also:

• FLAT (a modification of O. Eng. flet, an obsolete word of Teutonic origin, meaning the ground beneath the feet)

flat perforated bottom . In filtering into a vacuum the See also:

• FLASK

flask receiving the filtrate should be connected to the exhaust through a second flask .

The suction may be derived from any form of See also:

• AIR (from an Indo-European root meaning " breathe," " blow ")
• AIR, or ASBEN

air-See also:

• PUMP

pump; a form often employed where water at See also:

• FAIR

fair pressure is available is the See also:

• JET (Fr. jais, Ger. Gagat)

jet-pump, which in consequence is known as a filter-pump . Another method of filtering into a vacuum is to immerse a-porous See also:

• JAR

jar (" Pukall See also:

• CELL (from Lat. cella, probably from an Indo-European kal —seen in Lat. celare, to hide; another suggestion connects the word with Lat. cera, wax, taking the original meaning to refer to the honeycomb)

cell ") in the liquid to be filtered, and attach a suction-See also:

• PIPE

pipe to its interior . A filtering arrangement devised by F . C . See also:

• GOOCH, SIR DANIEL

Gooch, which has come into See also:

• COMMON

common use in quantitative See also:

• ANALYSIS (Gr. avci and Meta, to break up into parts)

analysis where the solid matter has to be submitted to heating or ignition, consists of a crucible having a perforated bottom . By means of a piece of stretched See also:

• RUBBER, INDIARUBBER

rubber tubing, this crucible is supported in the mouth of an See also:

• ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

ordinary funnel which is connected with an exhausting apparatus; and water holding in suspension See also:

• FINE

fine scrapings of asbestos, purified by boiling with strong hydrochloric See also:

• ACID (from the Lat. root ac-, sharp; acere, to be sour)

acid and washing with water, is run through it, so that the perforated bottom is covered with a layer of felted asbestos . The crucible is then removed from the rubber support, weighed and replaced; the liquid is filtered through in the ordinary way; and the crucible with its contents is again removed, dried, ignited and weighed . A perforated cone, similarly coated with asbestos and fitted into a conical funnel, is sometimes employed . In many processes of chemical technology filtration plays an important See also:

• PART

part . A crude method consists of straining the liquid through See also:

• COTTON
• COTTON (Fr. coton; from Arab. qutun)
• COTTON, CHARLES (163o–1687)
• COTTON, GEORGE EDWARD LYNCH (1813–1866)
• COTTON, JOHN (1585–1652)
• COTTON, SIR ROBERT BRUCE

cotton or other See also:

• CLOTH

cloth, either stretched on wooden frames or formed into long narrow bags (" bag-filters ") . Occasionally filtration into a vacuum is practised, but more often, as in filter-presses, the liquid is forced under pressure, either hydrostatic or obtained from a force-pump or compressed air, into a See also:

• SERIES (a Latin word from serere, to join)

series of See also:

• CHAMBERS (the Fr. chambre, from Lat. camera, a room)
• CHAMBERS, EPHRAIM (d. 1740)
• CHAMBERS, GEORGE (1803-1840)
• CHAMBERS, ROBERT (18oz-1871)
• CHAMBERS, SIR WILLIAM (1726-1796)

chambers partitioned off by cloth, which arrests the solids, but permits the passage of the liquid portions . For separating liquids from solids of a fibrous or crystalline See also:

• CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

character " hydro-extractors " or " centrifugals " are frequently employed .

The material is placed in a perforated cage or " See also:

• BASKET

basket," which is enclosed in an See also:

• OUTER

outer casing;._ and when the cage is rapidly rotated by suitable gearing, the liquid portions are forced out into the See also:

• EXTERNAL

external casing .