The Cannon-Fenske Viscometer

As an example of a simple modern capillary viscometer let us examine the Cannon-Fenske modification of the Ostwald viscometer, illustrated in Fig. 4-6. A specified volume of liquid is charged into the viscometer in the bottom reservoir A, and the liquid is then carefully drawn up through the capillary into the bulb B. The volume between the markers I and II is known precisely. The upper bulb T serves as a reservoir for the amount of liquid required to get the viscometer into steady-state operation. 

The quantities involved in the determination of viscosity are related by the following expression, obtained from the Hagen-Poiseui1le equation  

To calibrate the viscometer, a liquid of known viscosity is required. Determination of the absolute viscosity with the aid of Eqn 4-18 is discussed in detail by Hatschek [6] and by Reilly and Rae [7], with adequate descriptions of the apparatus and the techniques. Once Eqn 4-19 has been evaluated numerically for the calibrating liquid, the relation below follows directly  

The determination of kinematic viscosity with a calibrated viscometer rests on the following relation, derived from Eqn 4-20  

Thus once the viscometer has been calibrated, the kinematic viscosity of the liquid can be obtained directly from the outflow time and the calibration constant. 

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The Cannon-Fenske viscometer (Fig. 24b) is excellent for general use. A long capillary and small upper reservoir result in a small kinetic energy correction the large diameter of the lower reservoir minimises head errors. Because the upper and lower bulbs He on the same vertical axis, variations in the head are minimal even if the viscometer is used in positions that are not perfecdy vertical. A reverse-flow Cannon-Fen ske viscometer is used for opaque hquids. In this type of viscometer the Hquid flows upward past the timing marks, rather than downward as in the normal direct-flow instmment. Thus the position of the meniscus is not obscured by the film of Hquid on the glass wall. 

Capillary viscometers that have this design are called Ostwald viscometers. There are many specific designs of Ostwald viscometers. The most frequently used are the Cannon-Fenske viscometer... 

The Cannon-Fenske viscometer is used for measuring the kinematic viscosity of transparent Newtonian liquids, especially petroleum products and lubricants. The Ubbelohde viscometer is also used for the measurement of kinematic viscosity of transparent Newtonian liquids, but by the suspended level principle. 

Fig. 17.1 Two types of viscometers Ubbelohde (left) and Cannon-Fenske (right). The Ubbelodhe viscometer has the following components (1) fill tube, (2) capillary outlet, (3) pressure relief tube, (4) solution bulb, (5) suspended volume bulb, (6) lower flow bulb, (7) upper flow bulb, (8) upper timing mark, and (9) lower timing mark. The Cannon-Fenske Viscometer has the following components (1) fill tube, (2) capillary outlet tube, (3) solution bulb, (4) lower flow bulb, (5) upper flow bulb, (6) upper timing mark, and (7) lower timing mark.

Clean the Cannon-Fenske viscometer by placing the appropriate solvent into a solvent wash bottle. Continuously flush and aspirate the solvent through the viscometer until it is clean. 

The viscosity of the solutions was measured using the Cannon-Fenske viscometer. The foam tests were done by the conventional cylinder shake test In which a fixed amount of the solution Is shaken vigorously for a minute and the foam height Is monitored with time. The surface pressure measurements were carried out using a conventional Langmuir trough set-up, again with a platinum plate sensor. See text for further details. 

The Cannon-Fenske viscometer has two bulbs, and since the pressure head is different for each bulb, this allows qualitative assessment of the effect of shear stress 021 on the viscosity of the solution. The shear stress is given by... 

Capillary viscometers are simple and inexpensive. They are normally constructed from glass and resemble a U-tube with a capillary section between two bulbs. The initial design originated with Ostwald and is shown as part A in Figure 3.2-1. The Cannon-Fenske type, a popular modification of the Ostwald design that moves the bulbs into the same vertical axis, is shown as part B in Figure 3.2-1. 

Pectin lyase (PNL) activity was measured spectrophotometrically by the increase in absorbance at 235 nm of the 4,5-unsaturated reaction products. Reaction mixtures containing 0.25 ml of culture filtrate, 0.25 ml of distilled water and 2.0 ml of 0.24% pectin from apple (Fluka) in 0.05M tris-HCl buffer (pH 8.0) with ImM CaCl2, were incubated at 37 C for 10 minutes. One unit of enzyme is defined as the amount of enzyme which forms Ipmol of 4,5-unsaturated product per minute under the conditions of the assay. The molar extinction coefficients of the unsaturated products is 5550 M cm [25]. Also viscosity measurements were made using Cannon-Fenske viscometers or Ostwald micro-viscosimeter, at 37°C. Reaction mixtures consisted of enzyme solution and 0.75% pectin in 0.05 M tris-HCl buffer (pH 8.0) with 0.5 mM CaCl2. One unit is defined as the amount of enzyme required to change the inverse specific viscosity by 0.001 min under the conditions of reaction. Specific viscosity (n p) is (t/to)-l, where t is the flow time (sec) of the reaction mixture and t is the flow time of the buffer. The inverse pecific viscosity (n p ) is proportional to the incubation time and the amount of enzyme used [26]. Units of enzyme activity were determined for 10 min of reaction. 

Viscosity measurements were carried out using Cannon-Fenske viscometers of appropriate capillary diameter so as to keep the efflux time between 200-300 seconds. Approximate shear rate at the wall was calculated using the equation... 

The measurements were performed in an Ostwald Cannon-Fenske viscometer (No. J-627-25) using the method described by Silberberg and Klein Ci). This involves determining the time of flow as a function of the amount of liquid in the viscometer. Amounts between 7 and 8 g are chosen and the viscometer weighed to determine the exact amount. Buffer replacements were undertaken by dilution. 

A Cannon-Fenske viscometer is a capillary type of viscometer. It utilizes the flow through a capillary tube as a means of measuring viscosity. 

Solution Viscosity Studies. Ths polymer solution viscosity was run on two modified polymers and the original poly(vinyl alcohol) at 30°C in DMSO solutions using a series 100 Cannon-Fenske viscometer. The observed specific viscosities and the intrinsic viscosity for each of these samples are summarized in Table III. 

The Ubbelohde viscometer is shown in Figure 24c. It is particularly useful for measurements at several different concentrations, as flow times are not a function of volume, and therefore dilutions can be made in the viscometer. Modifications include the Cannon-Ubbelohde, semimicro, and dilution viscometers. The Ubbelohde viscometer is also called a suspended-level viscometer because the liquid emerging from the lower end of the capillary flows down only the walls of the reservoir directly below it. Therefore, the lower liquid level always coincides with the lower end of the capillary, and the volume initially added to the instrument need not be precisely measured. This also eliminates the temperature correction for glass expansion necessary for Cannon-Fenske viscometers. 

This protocol describes a method for measuring the viscosity of pure liquids and solutions by capillary viscometry. The sample is loaded into a Cannon-Fenske viscometer. The time required for the sample to flow between two time points on the viscometer is used to calculate the kinematic viscosity or viscosity. 

This method is an adaptation of the Basic Protocol for measuring the viscosity of pure liquids and solutions. The °brix (unithi.4) of the sample is adjusted to a desired value by dilution. In many protocols, a nominal value of 5 °brix is the accepted target value for dilution. The sample is then filtered to remove particles that would plug the capillary tube of the viscometer, and the serum viscosity is measured in a Cannon-Fenske viscometer. 

Many modifications of the basic Ostwald geometry are employed in different situations. One example is the Cannon-Fenske routine viscometer (Fig. 6.37b) which is used in the oil industry for measuring kinematic viscosities of 0.02 m2/s and less(4<). As viscosity is sensitive to variations in temperature, these types of viscometer are always immersed in a constant temperature bath. They are not normally suitable for non-Newtonian fluids although FAROOQI and Richardson(47) have employed a capillary viscometer to characterise a power-law fluid. 

Measuring Viscosity Several common methods are available for measuring viscosity. Two very common ones are the use of capillary tubes such as Ubbelohde, Ostwald, or Cannon-Fenske viscometer tubes and the use of a rotating spindle such as the Brookfield viscometer. 

Procedure Determine the flow time, in seconds, of the solvent (to) and of the three Sample Solutions (ti, t2, and t3, respectively) in a Cannon-Fenske viscometer immersed in a constant-temperature bath maintained at 130°. Calculate the specific viscosity, T sp, of each Sample Solution by the formula... 

Viscosity Determination. Viscosities were measured in 0.5 M cupriethylene-diamine (CED) at 25 °C with a Cannon-Fenske viscometer, size 100 (7). From these measurements, the intrinsic viscosity was determined according to the American Society for Testing and Materials (ASTM) Standard D1795. Values for the viscosity-average degree of polymerization were obtained by multiplying the intrinsic viscosity by 190. 

The viscosity of the oil was detenniaed using a Cannon-Fenske viscometer at 40 C. Density and refractive index were determined using hydrometers and a refractometer, respectively, at room temperature. Acid value, iodine number and saponification value were analyzed according to the Standard Methods of American OU Chemists. ... 

Table 4-1 shows some of the dimensions and operating characteristics of Cannon-Fenske viscometers. These particular instruments are designed for flow times in the range 200-1000 seconds. Capillary viscometer outflow time is governed partly by the acuity with which the transit of the... 

Viscosity Measurements. Solution viscosity data were obtained with the use of a Cannon-Fenske viscometer (size 50) at 25°C. Solutions were prepared in acetone (0.30 g/100 mL). 

Cannon-Fenske viscometer n. Capillary viscometer (calibrated) used for measuring relative flow time for liquids, useful for determining relative, specific and inherent viscosities of polymer solutions and extrapolation of intrinsic viscosities. It is convenient to clean and calibrate, but lacks correction due to different volume levels leading to weight due to gravity in the viscometer See image). 

Viscometers n. Instruments for measuring viscosity including mechanical probe and torque types as the Brookfield viscometer, capillary tube types as the Cannon-Fenske or Ostwald-Fenske, and flow through orifice types as the Ford cup. 

Experimental set-up and procedure Macroemulsions were produced by constant sonication for a period of about forty-five minutes in a thermostated bath at desired temperatures. Kinematic viscosity and specific conductance data of emulsions were obtained using standard Cannon-Fenske viscometer and conductivity meter, respectively. Bulk density and Screen factors of emulsions and equilibrated phases were determined by standard specific gravity bottles and screen viscometer, respectively. The interfacial tension values of oil/aqueous systems were measured by spinning drop technique. The details of measurement procedures are described elsewhere (4,5). 

Cannon Fenske viscometer or Ubbelohde viscometer) is also specified. The relative viscosity of the solution is determined by dividing the flow time of the polymer solution through a capillary viscometer by the flow time of pure solvent through the same viscometer at the same temperature conditions. 

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