Fine capillaries

Meanwhile fit up a Claisen flask (of about 175 ml. capacity) with a fine capillary and thermometer (see Fig. 12(A), p. 29), taking care that the range of temperature of 70°-100° is not obscured by the cork. Then filter the crude ester at the pump... 

The time is perhaps not yet ripe, however, for introducing this kind of correction into calculations of pore size distribution the analyses, whether based on classical thermodynamics or statistical mechanics are being applied to systems containing relatively small numbers of molecules where, as stressed by Everett and Haynes, the properties of matter must exhibit wide fluctuations. A fuller quantitative assessment of the situation in very fine capillaries must await the development of a thermodynamics of small systems. Meanwhile, enough is known to justify the conclusion that, at the lower end of the mesopore range, the calculated value of r is almost certain to be too low by many per cent. 

Polyolefin melts have a high degree of viscoelastic memory or elasticity. First normal stress differences of polyolefins, a rheological measure of melt elasticity, are shown in Figure 9 (30). At a fixed molecular weight and shear rate, the first normal stress difference increases as MJM increases. The high shear rate obtained in fine capillaries, typically on the order of 10 , coupled with the viscoelastic memory, causes the filament to swell (die swell or... 

When the superfluid component flows through a capillary connecting two reservoirs, the concentration of the superfluid component in the source reservoir decreases, and that in the receiving reservoir increases. When both reservoirs are thermally isolated, the temperature of the source reservoir increases and that of the receiving reservoir decreases. This behavior is consistent with the postulated relationship between superfluid component concentration and temperature. The converse effect, which maybe thought of as the osmotic pressure of the superfluid component, also exists. If a reservoir of helium II held at constant temperature is coimected by a fine capillary to another reservoir held at a higher temperature, the helium II flows from the cooler reservoir to the warmer one. A popular demonstration of this effect is the fountain experiment (55). 

In diying solids it is important to distinguish between hygroscopic and nonhygroscopic materials. If a hygroscopic material is maintained in contact with air at constant temperature and humidity until equilibrium is reached, the material will attain a definite moisture content. This moisture is termed the equilibrium moisture content for the specified conditions. Equilibrium moisture may be adsorbed as a surface film or condensed in the fine capillaries of the solid at reduced pressure, and its concentration will vaiy with the temperature and humidity of the surrounding air. However, at low temperatures, e.g., 15 to 50°C, a plot of equilibrium moisture content versus percent relative humidity is essentially independent of temperature. At zero humidity the equilibrium moisture content of all materials is zero. 

A 3-1. three-necked round-bottomed flask is fitted with a thermometer, a graduated dropping funnel (Note 1), a stirrer (Note 2), a fine capillary tube for introducing nitrogen near the bottom of the flask, and an exit tube attached through a ma-... 

A very delicate and useful piece of apparatus, which is leadily made with the blow-pipe, is Perkins modification of Sprengel s pyknometer. It is especially adapted for small quantities of liquid and for the moie volatile ones. The apparatus (Fig. 46) consists of a U l ube to hold from 2 to 10 c.c., drawm out at each end into a fine capillary. The one capillaiy limb, a, is bent outwards and is furnished with a small bulb the other, b, is bent at a right angle with the first. On the limb a, between the bulb and the top of the U-tnbe a mark is etched. The... 

Ten grams of the potassium salt of bromoauric acid (KBrA4) are dissolved in 100 cc of 96% ethyl alcohol. This salt is also designated as potassium auribromide. Sulfur dioxide (SO2) is then led through this solution, through a fine capillary tube, for several minutes. This reaction produces aurous bromide (AuBr). The solution of the aurous bromide is then allowed to... 

The total consumption type of burner consists of three concentric tubes as shown in Fig. 21.5. The sample solution is carried by a fine capillary tube A directly into the flame. The fuel gas and the oxidant gas are carried along separate tubes so that they only mix at the tip of the burner. Since all the liquid sample which is aspirated by the capillary tube reaches the flame, it would appear that this type of burner should be more efficient that the pre-mix type of burner. However, the total consumption burner gives a flame of relatively short path length, and hence such burners are predominantly used for flame emission studies. This type of burner has the advantages that (1) it is simple to manufacture, (2) it allows a totally representative sample to reach the flame, and (3) it is free from explosion hazards arising from unbumt gas mixtures. Its disadvantages are that (1) the aspiration rate varies with different solvents, and (2) there is a tendency for incrustations to form at the tip of the burner which can lead to variations in the signal recorded. 

Care is essential to avoid spillages. A fine capillary tube connected to a filter flask and filter pump should be used immediately to collect any spillage. Surfaces, e.g. floors, contaminated by minute mercury droplets should be treated with sulphur or zinc dust, or by use of a commercial clean-up kit. 

Fine capillary tubes may become blocked with water when blown into from the mouth it may be desirable to put a drying tube in the blowing tube or to blow with a rubber bulb. 

The seal is made by cutting 1-cm diameter tubing to give one piece with a square end. Near the end of the other piece a spindle is drawn. The shoulder of the spindle is heated in a small hot flame so that it thickens, and then, with a fairly cool flame, the spindle beyond the shoulder is drawn out to a fine capillary about 1 mm diameter. This is heated in a very cool flame and bent first one way and then the other, as m Figure 47, II. The end is finally sealed off. The tip thus prepared is inserted into the square end of the other piece of tubing, as in Figure 47, /, and a joint is made by directing a small flame at... 

The electrokinetic processes can actually be observed only when one of the phases is highly disperse (i.e., with electrolyte in the fine capillaries of a porous solid in the cases of electroosmosis and streaming potentials), with finely divided particles in the cases of electrophoresis and sedimentation potentials (we are concerned here with degrees of dispersion where the particles retain the properties of an individual phase, not of particles molecularly dispersed, such as individual molecules or ions). These processes are of great importance in particular for colloidal systems. 

A very fine capillary tube should be used. It is better to conduct the distillation in a stream of an inert gas, such as hydrogen or nitrogen. 

In the case of epoxide cements at temperatures lower than 20° C, the viscosity increases so much that pumping becomes difficult [342]. Small amounts of aromatic solvents reduce the viscosity satisfactorily. Ethylene glycol butyl ether also changes the interfacial tension so that the polymer may penetrate into hairline cracks and fine capillaries. This is advantageous in blocking liquid or gas migration. 

Precipitation and accumulation of clay. Precipitation of clay particles takes place at some depth in the soil as a result of 1. flocculation of clay particles, or 2. (mechanical) filtration of clay in suspension by fine capillary pores. 

In TLC, a 10- iL or larger syringe is often used to place sample spots on the thin layer before development. Alternately, a glass capillary tube or Pasteur pipette may be heated in a burner and pulled to obtain a fine capillary suitable for spotting (see Figure 13.3). 

In order to prepare absolute ether the commercial product (1-2 L) is first dried for one to two weeks over calcium chloride (weight about 10 per cent of the weight of the ether taken) and poured rapidly through a folded filter into a dry flask into which sodium wire is driven from a press. Until the evolution of hydrogen ceases, a calcium chloride tube, drawn out to a fine capillary so as to reduce the... 

After passing through the boundary layer, the molecules of adsorbate diffuse into the complex structure of the adsorbent pellet, which is composed of an intricate network of fine capillaries or interstitial vacancies in a solid lattice. The problem of diffusion through a porous solid has attracted a great deal of interest over the years and there is a fairly good understanding of the mechanisms involved, at least for gas phase diffusion. Here, diffusion within a single cylindrical pore is considered and, then, the pore is related to the pellet as a whole. 

The selection of the diffusion material is a subject of considerable difficulty, if the porosity of the material is too great no diffusion takes place, but the gas passes through the material without any appreciable separation taking place. Thus, if a mixture of hydrogen and oxygen is passed through a fine capillary tube, the gas... 

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