Viscosimeter Ostwald

Endo-pectinases were determined by reduction of viscosity of a 1% (w/v) pectin solution at 30 C and pH 4.2 using an Ostwald viscosimeter as previously described (9). One unit was defined as the amount of enzyme which reduced the initial viscosity of the solution by 50%. 

Ostwald viscosimeter two 100- and two 250-mL volumetric flasks a 10- and a 50-mL pipette pipetting bulb 250-mL glass-stoppered flask one 100- and two 250-mL beakers stirring rod hot plate thermometer stopwatch or timer length of gum-rubber tubing. If polymer stock solution is to be prepared by the student weighing bottle funnel Pyrex wool. 

After the oxidation, a portion of the reaction mixture was placed on a polystyrene sheet and dried at 60 °C overnight to obtain a film, that was analyzed by ir spectroscopy. The viscosities of unoxidized and oxidized PVA were determined at 45 °C in water with a modified Ostwald viscosimeter. 

There have been many polemics as to the applicability of the Staudinger rule which, however, need not be discussed here after what has already been said on the limits of the method. As regards the carrying out of viscosity measurements, the OsTWALD viscosimeter is a suitable apparatus. For the requirements as to the dimensions of the instrument we may refer to papers of Bungenberg de Jong and Schulz . Ekenstamm has given a simple formula to correct for the difference in density between solvent and solution. ... 

Kinematic viscosity may be determined directly by means of Ubbelohde, FitzSimmons modification, or modified Ostwald viscosimeter pipettes (D445). A series of these pipettes which cover the entire useful range of viscosity may be suspended in a single constant-temperature bath. Great accuracy is possible with these instruments, and a somewhat smaller sample is satisfactory, but each instrument must be calibrated. The pipette method must be used for gasoline, naphthas, or kerosene, because turbulent rather than streamline flow occurs in the large orifices of the Saybolt equipment. The viscosity of kerosene is sometimes determined in the Saybolt thermoviscosimeter, and thermoviscosity (at 60 F) is related to the kinematic and Saybolt Universal viscosity (at 60 F) approximately as follows ... 

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. 

CN 06897, and Rohm Tech Inc., Malden, MA 02148. All preparations were assayed for polygalacturonase (PG), cellulase, and pectinesterase (PE) activities by the methods of Vas, et al. (6 ) as modified by Bruemmer et al. ( ] ). PG and cellulase activities were determined by reduction of specific viscosity in an Ostwald-type viscosimeter held in a 50°C water bath. PG activity was measured on both 1.5% polygalacturonic acid (U.S. Biochemical Corp.), titrated... 

FIGURE 5.203 Capillary tube viscosimeters used to measure kinematic viscosity (a) modified Ostwald, (b) Ubbelohde, (c) Fitz Simmons. (Gulf Oil Corporation.)... 

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