Mixing Measures

Fig. 2-7. Mixing measured volumes of hydrogen chloride gas and ammonia gas.

The mixed cmc behavior of these (and many other) mixed surfactant systems can be adequately described by a nonideal mixed micelle model based on the psuedo-phase separation approach and a regular solution approximation with a single net interaction parameter B. However, the heats of micellar mixing measured by calorimetry show that the assumptions of the regular solution approximation do not hold for the systems investigated in this paper. This suggests that in these cases the net interaction parameter in the nonideal mixed micelle model should be interpreted as an excess free energy parameter. 

Hellen L, Yliruusi J. Process variables of instant granulator and spheroniser III. Shape and shape distributions of pellets. Int J Pharm 1993 96 217-223. Chapman SR, Rowe RC, Newton JM. Characterization of the sphericity of particles by the one plane critical stability. J Pharm Pharmacol 1988 40 503-505. Rowe RC, Sadeghnejad GR. The rheology of mcc powder/water mixes-measurement using a mixer torque rheometer. Int J Pharm 1987 38 227-229. O Connor RE, Schwartz JB. Spheronization II Drug release from drug-diluent mixtures. Drug Dev Ind Pharm 1985 11 (9-10) 1837-1857. 

Figure 3. Block diagram of the experimental apparatus for an optical mixing measurement...

Nonlinear optical studies were carried out using a combination of nonlinear absorption, self-focusing and degenerate four wave mixing measurements. The measurements were made using a Quantel Nano-Pico system that permits operation at either 10 ns or 100 ps pulse lengths at 1064 nm. The 10 ns pulses were TEM mode and temporally smoothed to a near gaussian (H). 

The superscripts, 1 and c, in Table I identify linear and circular polarised light respectively. Since the nanosecond measurements were dominated by molecular rotation in the dithiolene complexes, degenerate four wave mixing measurement were carried out using 100 ps pulses to measure the electronic contribution directly. 

In a 3 (Group) x 2 (Consistency) x 2 (Metaphor type) x 3 (Context Word type) mixed-measures ANOVA effect of Consistency was marginally significant, F(l, 69) = 3.74,/) = 0.057. Further, the effect of Consistency was significant when the same condition was removed and the analysis performed over only the opposite and neutral conditions. 

For sample blanks, transfer 2.0 mL of the Sample Solution and 3.0 mL of the Sodium Carbonate Solution into a test tube, and mix. Add 2.0 mL of PNPG Solution, and mix. Measure the absorbance of each sample and the blank versus water in a 10-mm cell. 

It is critical to recognize the high reactivity and low stability of anthocyanins in the selection of methods of extraction and quantitation in the analysis of anthocyanins. An analysis of processed samples containing anthocyanins for polymeric color as well as monomeric anthocyanins is recommended in nutrition studies until we better understand any health effects (positive or negative) of the compounds that are part of the mix measured as polymeric color. ... 

There are several different ways of obtaining an estimate of the interaction between two polymers. These include heat of mixing measurements, inverse gas chromatography, solvent vapour absorption, various scattering techniques and viscosity... 

Fig. 16. Heat of mixing measurements for mixtures of secondary octyl acetate with a chlorinated paraffin (used as analogues for an ethylene-vinyl acetate copolymer and chlorinated polyethylene) at 64.5 °C (x), 73.1 °C(0) and 83.5 °C ( ) as a function of composition. The heat of mixing is very temperature dependent and the composition dependence is not as would be expected from the Equa-tion-of-state theory. This will result in a temperature and composition dependence of the interactional parameter...

A second issue is that there is necessarily a trade-off between precision and resolution. That is, if the box sizes are reduced, one obtains more boxes and hence more values of Ca, and consequently any mixing measure will in principle have a lower standard error. On the other hand, this reduction has an obvious limit as the box size approaches the grain size, at which point any blend will statistically appear to be unmixed (because each box can only take on one of the two values, Ca = 0 or Ca = 1). In practice, a happy medium delivering both suitably low standard error and an adequate sample size is easily achieved nevertheless it is important to understand what it is that one is seeking to obtain before deciding on a sampling protocol. 

Fig. 14 Illustration of the importance of rational data interpretation. The state (B) intuitively looks well mixed, but has the same number of black and white boxes as states (A) and (C). Evidently a larger box size is required to make meaningful mixing measurements. States (B) and (C) have very different structures, but produce similar measures of mixing using common statistics. For this reason, many customized mixing measures have evolved in the literature.

Two other mixing measures of importance to pharmaceutical processing are, first, the relative standard deviation (RSD), defined to be ... 

To examine the behavior of mixing measures, it is useful to begin by considering systems free of experimental uncertainties. Particle dynamic simulations such as those discussed in the sections Mixing mechanism in Three Dimensional Tumblers and Demixing, represent such ideal systems the presence and locations of all particles are known and are free of sampling errors (discussed in the section on Sampling Techniques ). 

Rowe, R.C. Sadeghnejad, G.R. The rheological properties of microcrystalline cellulose powder/water mixes-measurement using a mixer torque rheometer. Int. J. Pharm. 1987, 38, 227-229. 

All these solutions exhibit essentially the same characteristics, the activity coefficients are less than unity and the heat of mixing, measured... 

Mix by tapping and cover with evaporation caps. Place tubes in boiling water bath for 15 minutes and then cool in cold water for 5 minutes. Add 5 ml of 60% ethanol. Mix. Measure the colors in a photoelectric colorimeter with a Klett No. 56 filter or in a spectrophotometer set at 570 nm against a reagent blank. 

Distelhoff M.F., Marquis A.J., Nouri J.M., Whitelaw J.H., Scalar Mixing Measurements in Batch Operated Stirred Tanks, Canadian... 

Determination of Fe. Add 7 ml of the ECR solution and 3 ml of the CTA solution to a sample solution (pH 1-2) containing not more than 8 pg of Fe. Adjust the pH to - 4 with dilute ammonia and add 5 ml of acetate buffer. Transfer the solution to a 25-ml standard flask, dilute with water to the mark, and mix. Measure the absorbance of the solution at 610... 

Our present understanding of mixing and UVR effects has been limited by both the availability of physical measurements and the oversimplified representation of mixing processes in experiments and analyses. This is expected to change in the future as it becomes more practical to incorporate mixing measurements into field work, and as experimental exposures and mixing models become more sophisticated and allow a better approximation of actual water column conditions. 

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