Efflux Time Research Articles

Effect of Wall Surface on Capillary Flow

Among various methods of viscosity measurement, the capillary methods are the most usual ones, by which the coefficient of viscosity is obtained on the assumptions that there is no slip at the capillary wall and that the fluid is homogeneous throughout the capillary, and so on.So it is important to study first of all whether these assumptions hold or not in the actual flow. As regards the wall effect, measurements of the flow of various liquids using capillaries of different materials have hitherto been reported, but some of them are of doubtful accuracy and ambiguous in details of their experiments.To obtain systematic and accurate data on this problem, measurements were made of efflux time of ion-exchanged water, human blood and plasma, using an Ostwald type viscometer with and without paraffine coating.Correction in the thickness of the paraffine layer was made based on the Hagen-Poiseuille equation. Moreover, the change of the efflux time with the time elapsed was measured by using another capillary at the same time as shown in Figs. 1 (B) and 2 (B) to correct the effect due to denaturation of the samples such as blood and plasma.The result shows that the efflux time is slightly increased by the paraffine coating and the order of the increase is as follows: water (-0.92∼+1.64%)<plasma(+0.15∼+2.54%)<blood(-0.56∼+4.2%).

魚肉アクトミオシンの粘度に関する研究-I

Some fundamental problems concerning the viscosity of actomyosin were studied by using a tilting viscometer (Fig. 1) designed by WADA3), in which control of velocity gradient of the flow can be readily practiced simply by changing the position on the supporting plate to which the curved end of the viscometer is fixed. Relative viscosity ηγ and velocity gradient ?? are calculated from equations (1) and (2) respectively, where to and ts are efflux times of solvent and solution, respectively. V and R in equation (2) are the efflux volume and the radius of the capillary, respectively. Viscosity of carp actomyosin solution prepared according to Table 1 was measured at varying velocity gradients ( ?? ) and concentrations (c). Some one hour was required for the whole measurement, but the solution proved to be stable at least for one hour at 10°C. (Table 2) and 20°C. Apparent decrease in viscosity was observed with increasing velocity gradient (Fig. 2), as already reported by many workers with rabbit1, 2) and carp6) actomyosins. At quite a low velocity gradient ( ?? <100 sec-1), however, ηγ showed a fixed value independent of ?? at any concentration studied (0.03-0.25%) as illustrated in Fig. 2. This is not concordant with the result obtained by HAMOIR who measured viscosity of carp actomyosin under varying pressures form 0 to 15cm. of water by means of a capillary tube equipped with an air reservoir. On the other hand, the same results as ours have been obtained with nitrocellulose in butyl acetate and polystyrene in toluene as well as tobacco mosaic virus in water7). The reason of the disagreement between the result of HAMOIR and ours is obscure. Intrinsic viscosity [η] of carp actomyosin was determined from ηsp/c or In ηγ/c by extrapolating both c and ?? to zero and was found to be 2.0-6.0 (Fig. 3). Measuring temperature seemed to exert an influence hardly or but slightly, if any, on intrinsic viscosity of carp actomyosin; [η]=2.5 at 5°C., and 2.2 at 20°C. were obtained with one and the same preparation (Fig. 5). Viscosity number Zη=(2.3 log ηγ)/c is often conveniently used as a substitute of intrinsic viscosity. Since, however, in carp actomyosin no linearity was found except one out of a dozen cases in the relationship between In ηγ and c at least within our experimental conditions (Fig. 4), viscosity number cannot be a characteristic quantity independent of experimental conditions. Similarly in carp actomyosin at least within our experimental conditions, ATP-sensitivity, Zη-ZηATP/ZηATP, proposed by PORTZEHL et al cannot be taken significant in characterizing an actomyosin preparation, independently of experimental conditions. The initial slope of the curve (ηsp/c)c→o- ?? or (In ηγ/c)c→o- ?? affords a rough measure of the readiness with which the molecules are orientated, that is the shape of the molecule; and the initial slope of the curve (ηsp/c) ?? →o-c or (In ηγ/c) ?? →o-c offers some knowledge about the extent of intermolecular interaction (cf. Fig. 6).

Precision viscometry of polyvinyl acetate in toluene

AbstractThe viscosity of dilute solutions of PVA in toluene is investigated as a function of shearing stress in an Ubbelohde precision viscometer which permits determining the efflux time to within 3 × 10−3 sec. Various sources of error in capillary viscometry are discussed. Correction for drainage is made on the basis of a newly developed theory. In a first series of measurements uncorrected values of (t − t0)/t0c are shown to give an anomalous curve when plotted against c. In this series the effect of changes in concentration as a result of adsorption onto the walls of the dilution vessels is studied. The anomaly disappears when corrections are made for various sources of error and for non‐Newtonian behavior in particular (second series). The thickness of the adsorption layer on the wall of the capillary is estimated from results in two viscometers with different bore. A comparison with direct measurements of adsorption on glass beads reveals that the average density of the polymer adsorbed is about 0.17 g./ml. The viscosity at low shearing stress is an even function of the shearing stress. The intrinsic viscosity is markedly dependent on shear rate, its value at high shear rates being about 40% of that of zero shear rate.

Magnetic susceptibility data for some biologically important derivatives of phenanthrene

Experiments show that during the thermal DNA denaturation process an applied magnetic field of 10 kG increases the shear viscosity (measured efflux time) of calf thymus DNA in 0.0172 M KCI solution over the viscosity of the same solution at the ambient earth field (or “no” field) condition. There is also observed an increase (although slight, about 0.1°C) in the thermal denaturation temperature of the process.

氣體流出に関する熱力學的研究

This paper is relate to an experiment to determine the coefficient of discharge of gas through a nozzle and orifice etc. by the method of measuring the time of efflux of air from a vessel. Notwithstanding that the correct measurement of the temperature change of the air in the vessel is the atmost important thing in this mothod, because it affects the coefficient very severely yet the radiation effect fails the measurement almost to nonsense. In this research the author has made an attempt to measure the correct temperature by the following method : the air which is filled in the vessel with certain pressure and temperature is discharged by opening the cock until it reaches to a certain pressure and the cock is then rapidly closed. After the cock is closed, the pressure and temperature of the air rise gradually and reach finally to a steady condition. The pressure and temperature are then read, and the temperature at the instant when the cock was closed is calculated from the perfect gas law by using these values. The vessel is then filled with the compressed air at the original pressure and temperature. Discharge is made again until another pressure is reached and the temperature at that instant is calculated by the same method as above described. The temperature change thus obtained is shown in the Fig. 7 comparing with that obserbed by the oscillograph. Experiments were repeated changing the initial pressure ; and the coefficients calculated both from the observed and calculated temperatures are compared in the Fig. 11 showing the defect of the value calculated from the former. The coefficients of discharge of the nozzle, sharp orifice and flat edged orifice are compared in the Fig. 12. The coefficient of discharge decreases with the pressure, as shown in the Fig. 12,and especially those of the sharp orifices decrease rapidly at about the critical pressure while the decreasing of those of the nozzles and flat edged orifices are not so remarkable.

On the conditions at the boundary of a fluid in turbulent motion

The experiments here described form part of a general research into the phenomena of skin friction of solid surfaces due to the flow over them of fluids whose motion, not in the immediate vicinity of the surface, is eddying or turbulent. Considerable information has been obtained in recent years as to the magnitude of the frictional forces brought into existence in this condition of flow, and the manner of variation of these forces with the relative mean speed of surface and fluid, the roughness of the surface, and the physical characteristics of the fluid is fairly well known. Practically nothing, however, is known about the mechanism by which the resistance to flow is transmitted to the bounding surfaces. For speeds below the critical when the general motion of the fluid throughout is streamline in character, it is generally accepted that the layer of fluid in contact with the boundary is at rest relative to it, as any slipping of finite amount would be detected in a variation from the Poiseuille law of the relationship between the diameter of a pipe and the time of efflux of a given volume of fluid. At speeds above the critical, observations near the walls have shown that the mean velocity falls rapidly as the solid bounding surface is approached, and it has been suggested that at the walls there may exist a thin layer in which the flow is laminar in character, in which case, if there is no slipping, the frictional resistance would be determined from the slope of the velocity curve in the surface layer and the coefficient of viscosity of the fluid. During the last few years several attempts have been made at the National Physical Laboratory to obtain evidence as to the truth of this assumption. The method adopted has been to set up a condition of turbulent fluid motion over a surface of which the frictional resistance to the flow could be accurately determined, and to measure by means of a very fine Pitot tube the velocity of the fluid at a point as near the wall as possible.