Filtration purpose

Yarn and monofilament only staple plus tow included under other. c Does not include fiber produced for cigarette filtration purposes. d Includes saran and Spandex yarn also, olefin and vinyon staple and tow. 

Non-glazed earthenware is used for special filtration purposes (diaphragms, bacteriological filters). 

The word membrane here stands for a thin polymn film which for the types used to today is characterized by a heterogeneous (asymmetric) structure, while the films used for filtration purposes have pores of even diameto all through the membrane. There is as yet no generally accepted scientific explanation of gas transport through polymer membranes. Attempts at describing these processes by... 

In practice, the manufacturers of multifilament yams produce a number of standard linear densities that, for industrial filtration purposes, may range in fineness from 120 decitex to 2200 decitex, with individual filaments varying from 6 to 10 decilex. From this, it can be shown that the diameter of such filaments will be of the order of 0.03 mm. 

Filtration properties are effected by the nonwoven fabric production properties. For the filtration purposes depending on the size of the particulate to be filtered, fabric thickness plays quite important role moret titan other properties. 

There are several available weaves of woven wire. Some of these weaves lead the product to be called woven fabric. The basic types of weaves of wire cloth, which are woven for filtration purposes, are plain, twilled, plain Dutch, twilled Dutch, plain reverse Dutch, duplex (twin warp) plain Dutch, Betamesh and braided (basket of multibraid)—see Figure 8.1. 

Recently some very precise filters made from a bundle of fibres in a glass matrix has been developed by Collimated Holes Incorporated [54]. To make these filters a bundle of fiber optics is assembled in a glass matrix with the core of a fiber perpendicular to the surface of the matrix. The assembled plate is then treated with a fluid to dissolve the central core of the fibre optics which are chemically different from the glass matrix. The resultant porous surface has very accurate holes for filtration purposes. 

A FIA indirect method was described for saccharin determination by Yebra et al. [88]. This method was based on the precipitation of silver saccharinate in an acetic acid medium. The precipitate was dissolved in ammonia, and the dissolved silver was continuously measured by FA AS. The FIA precipitation-dissolution manifold used is similar to that used for cyclamate determination [83] however, in this work, a Scientific System 05-105 column fitted with a removable screen-type stainless-steel filter (pore size 0.5 pm, chamber inner volume 580 pL, filtration area 3 cm ), originally designed as a cleaning device for liquid chromatography, was employed for filtration purposes. 

For some, undemanding, applications, a simple felt can provide suitable filtration performance, without any form of strengthening. However, their low tensile strengths, and the ease with which fibres can become detached, make simple felts unattractive for most filtration purposes, and some mechanical (or chemical) strengthening is required. 

For filtration purposes, the most widely used forms of woven wire are the Dutch or hollander weaves, wherein the warp and weft are of different diameter, generally with a corresponding difference in the relative numbers of warp and weft wires. If the warp wires are thicker, the result is the plain Dutch weave the alternative is for the weft wires to be the thicker, giving the reverse plain Dutch weave . 

The oxime is freely soluble in water and in most organic liquids. Recrystallise the crude dry product from a minimum of 60-80 petrol or (less suitably) cyclohexane for this purpose first determine approximately, by means of a small-scale test-tube experiment, the minimum proportion of the hot solvent required to dissolve the oxime from about 0-5 g. of the crude material. Then place the bulk of the crude product in a small (100 ml.) round-bottomed or conical flask fitted with a reflux water-condenser, add the required amount of the solvent and boil the mixture on a water-bath. Then turn out the gas, and quickly filter the hot mixture through a fluted filter-paper into a conical flask the sodium chloride remains on the filter, whilst the filtrate on cooling in ice-water deposits the acetoxime as colourless crystals. These, when filtered anddried (either by pressing between drying-paper or by placing in an atmospheric desiccator) have m.p. 60 . Acetoxime sublimes rather readily when exposed to the air, and rapidly when warmed or when placed in a vacuum. Hence the necessity for an atmospheric desiccator for drying purposes. 

Recrystallise from methylated spirit, using animal charcoal for this purpose, use about twice the minimum quantity of methylated spirit required to obtain a clear solution, and filter through a funnel preheated by the filtration of some boiling solvent, as the tribromobenzene separates very rapidly as the solution cools. The 1,3,5-tribromobenzene is thus obtained as colourless crystals, m.p. 122° yield, 3 g. 

In a 1-litre three-necked flask, fitted with a mechanical stirrer, reflux condenser and a thermometer, place 200 g. of iodoform and half of a sodium arsenite solution, prepared from 54-5 g. of A.R. arsenious oxide, 107 g. of A.R. sodium hydroxide and 520 ml. of water. Start the stirrer and heat the flask until the thermometer reads 60-65° maintain the mixture at this temperature during the whole reaction (1). Run in the remainder of the sodium arsenite solution during the course of 15 minutes, and keep the reaction mixture at 60-65° for 1 hour in order to complete the reaction. AUow to cool to about 40-45° (2) and filter with suction from the small amount of solid impurities. Separate the lower layer from the filtrate, dry it with anhydrous calcium chloride, and distil the crude methylene iodide (131 g. this crude product is satisfactory for most purposes) under diminished pressure. Practically all passes over as a light straw-coloured (sometimes brown) liquid at 80°/25 mm. it melts at 6°. Some of the colour may be removed by shaking with silver powder. The small dark residue in the flask solidifies on cooling. 

Equip a 1 Utre three-necked flask or a 1 litre bolt- head flask with a reflux condenser and a mercury-sealed stirrer. Dissolve 50-5 g. of commercial 2 4-dinitro-l-chlorobenzene in 250 ml. of rectified spirit in the flask, add the hydrazine solution, and reflux the mixture with stirring for an hour. Most of the condensation product separates during the first 10 minutes. Cool, filter with suction, and wash with 50 ml. of warm (60°) rectified spirit to remove unchanged dinitrochlorobenzene, and then with 50 ml. of hot water. The resulting 2 4-dinitrophenylhydrazine (30 g.) melts at 191-192° (decomp.), and is pure enough for most purposes. Distil oflF half the alcohol from the filtrate and thus obtain a less pure second crop (about 12 g.) recrystallise this from n-butyl alcohol (30 ml. per gram). If pure 2 4-dinitrophenylhydrazine is required, recrystallise the total yield from n-butyl alcohol or from dioxan (10 ml. per gram) this melts at 200° (decomp.). 

In a 1 litre round-bottomed flask, equipped with an air condenser, place a mixture of 44 g. of o-chlorobenzoic acid (Section IV,157) (1), 156 g. (153 ml.) of redistilled aniline, 41 g. of anhydrous potassium carbonate and 1 g. of cupric oxide. Reflux the mixture in an oil bath for 2 hours. Allow to cool. Remove the excess of aniline by steam distillation and add 20 g. of decolourising carbon to the brown residual solution. Boil the mixture for 15 minutes, and filter at the pump. Add the filtrate with stirring to a mixture of 30 ml. of concentrated hydrochloric acid and 60 ml. of water, and allow to cool. Filter off the precipitated acid with suction, and dry to constant weight upon filter paper in the air. The yield of iV-phenylanthranilic acid, m.p. 181-182° (capillary tube placed in preheated bath at 170°), is 50 g. This acid is pure enough for most purposes. It may be recrystaUised as follows dissolve 5 g. of the acid in either 25 ml. of alcohol or in 10 ml. of acetic acid, and add 5 ml. of hot water m.p. 182-183°. 

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