Apparatus with NaCl concentration

Fig. 4. Gel filtration (Sephadex G-75) of the soluble proteins from pig brain which are eluted from ECTEOLA cellulose at a NaCl concentration between 0.1 M and 1 M. The proteins in this fraction were concentrated in a Diaflo apparatus and incubated with 25 fid 45CaCl2 before gel filtration. Absorbancy at 750 M following Lowry reaction (—) radioactivity (---). From Ref. (159)...

Figure 11.36 gives such plots, which clearly show that W decreases with increasing NaCl concentration, reaching a minimum above 10 mol dm , whereby maximum deposition occurs. Similar results were obtained by Tadros et al. [45] using a rotating cylinder apparatus (Figure 11.37). 

These studies were performed at high surfactant concentrations (> 0.01 mol dm 3) where the appearance of -potential was hard to explain. Unclear remained the fact that f-potential did not depend on the electrolyte concentration (NaCl) up to a value of 3%. Anomalously high values of -potential ( 0.5 V) have been reported by Laniquielli and Galembeck [64] who studied electrokinetic phenomena occurring at gravitational foam drainage. They attribute this anomaly to the electrolyte accumulation in the electrode space. The analysis of these results indicates that reliable values of the -potential in foams can be derived with an especially developed theory of the electrokinetic phenomena in foams that accounts for the peculiarities of these systems. Furthermore, new apparatus is needed to allow the study of foams with controlled border sizes and precisely defined border profile. 

In the isopiestic method, the vapor pressure of a solution is determined by equilibrating it with that of a reference solution (aqueous NaCl is often used) whose vapor pressure as a function of salt concentration and temperature is well known. This method can provide osmotic coefficients accurate to better than 1% over a wide range of conditions, but it is accurate only for electrolyte molalities above approximately 0.1 mol kg. The necessary equilibration may take several days, and specialized apparatus is required for measurements significantly above room temperature. 

You are given a soluble compound of unknown molecular formula, (a) Describe three tests that would show that the compound is an acid, (b) Once you have established that the compound is an acid, describe how you would determine its molar mass using a NaOH solution of known concentration. (Assume the acid is monoprotic.) (c) How would you find out whether the acid is weak or strong You are provided with a sample of NaCl and an apparatus like that shown in Figure 4.1 for comparison. 

Calorimetric measurements at a salt concentration of 0.8 M (NaCl) were carried out with a differential scanning microcalorimeter microDSC III (Setaram, Caluire, France). The melting of naphthalene was used to calibrate the apparatus. The sample cell was filled with 850 mg carrageenan solution (0.2% w/w in 0.8M NaCl) and the reference cell with exactly the same amount of NaCl solution. Heating and cooling curves were recorded in the temperature range from 10 to 120°C at a rate of 1.0°C min-1. 

Shear Wave Propagation. A pulse shearometer (Rank Bros.) was used to measure the propagation velocity of a shear wave through the weak gels formed by the solutions of HMHEC in dilute NaCl. The polymer concentration range studied was 0.5-2.0%. With this apparatus, the frequency of the shear wave is approximately 1200 rad s" and the strain is <10 . At this strain, n pst systems behave in a linear viscoelastic fashion, and the wave-rigidity modulus, G is... 

Evaluation of HA molar mass ehanges was performed with Shimadzu apparatus using a packed HEMA-BIO 1,000 colunm of dimensions 7.8 mm x 250 mm, the packing particle size was 10 pm. The mobile phase 100 mM phosphate buffer (pH 7.0) containing 0.15M NaCl was pumped by the LC-IOAD device at a flow rate of 0.5 ml/min. For catibration of the SEC system used reference HAs (M = 90.2-1380 kDa) with broader molar mass distributions (M /M = 1.60-1.88) were apphed. The samples of the volume of 20 pi with the polymer concentrations 1 mg/ml or lower were injected by a 7725i-type Rheodyne valve. The SEC analyses performance was monitored online by UV (SPD-IOAV, set at 206 run) and refractive index (RID-10) detectors. 

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