Sodium alginate solution

The flow properties of sodium alginate solutions depend on concentration. A 2.5% medium viscosity sodium alginate solution is pseudoplastic, especially at the higher shear rates in the range of 10—10,000/s. 

Wet cells (5g) are suspended in 15 ml of a 1% sodium alginate solution. The mixture is then forced through a syringe needle into a 0.05 M CaCl2-solution containing the necessary nutrients for the cell. Gelation occurs almost immediately. 

The viscosity of sodium alginate solutions is slighdy depressed by the addition of monovalent salts. As is frequendy the case with polyelectrolytes, the polymer in solution contracts as the ionic strength of the solution is increased. The maximum viscosity effect is obtained at about 0.1 N salt... 

Polysaccharides from plants, too, can form gels in water. Pectin is used to help gel jams and fruit preserves. Some polysaccharides are used to thicken foods. Alginic acid, extracted from brown algae, is a linear polymer containing many carboxylic acid groups. The sodium salt is soluble in water and is used as a thickener in the preparation of ice cream and other foods. If a sodium alginate solution is mixed with calcium ion, the polysaccharide pre-... 

While alginate salts with alkali metals such as sodium or potassium are soluble in water salts with divalent cations such as calcium, copper and zinc (Ca2+, Cu2+, and Zn2+, respectively) are insoluble in water. In this experiment, you will observe what happens when a drop of a sodium alginate solution is added to an aqueous solution of a divalent cation. The transformation from polymer solution to gel involves the concepts of polymer solubility, diffusion, and ion exchange. 

A. Precipitation. Add 1-2 mL of 2% sodium alginate solution to 10 mL of 1M HC1 solution in a test tube or vial and stir or shake. Note your observations. 

C. Alginate "Snakes" This makes an excellent demonstration on an overhead projector. Fill a crystallizing dish or beaker to a depth of Vi to 3A inch with 2% Ca(N03)2 solution. Introduce a stream of 2% sodium alginate solution directly into the- Ca2+ solution using a pipet. You should be able to cause the formation of a long strand of gel (a snake ). For the most part, the properties of the strands should be the same as those of the beads that you explored above. To test the physical properties of your snakes, wash them in fresh water and let them dry. As they are drying, periodically test their strength and note their appearance. 

Fig. 1.13. Histograms of bubble size distribution (a) - foam from Teepol and sodium alginate solution ...

Dropping or spraying a sodium alginate solution into a calcium chloride solution produces microcapsules. The divalent calcium ions cross-link the alginate, forming gelled droplets. These gel droplets can be permanently cross-linked by addition to a polylysine solution. Lim and Sun developed this method for the encapsulation... 

Bugaj J, Gorecki M. Kinetics of dynamic viscosity changes of aqueous sodium carboxymethylcellulose and sodium alginate solutions. Pharmazie 1995 50(11) 750—752. 

The viscosity of sodium alginate solutions increases very rapidly with concentration, as the viscosity-concentration curves for alginates of different grade de-... 

Table VI. Viscosity of Sodium Alginate Solutions at Various Concentrations...

The weight of sodium alginate in solution equals the volume of sodium hydroxide X 0.1 X 0.1981 grams. The titrated solution was then weighed and diluted with water to give a 0.25% (w./w.) sodium alginate solution, sodium chloride was added to bring the normality to 0.1, and the viscosity was measured at 25 C. in Ostwald viscometers (j )-... 

The sodium chloride was added to eliminate the electroviscous effect shown by sodium alginate solutions (6, 11, 12), Rose (11) found that O.IN sodium chloride swamped this effect, and higher concentrations, up to 0,5N sodium chloride, either had no additional effect or slightly increased the viscosity of 0.1 to 0.5% solutions of sodium alginate. 

Condensed ion effects. The enthalpy of mixing of a polyelectrolyte and a simple salt containing different counterions was next investigated. Sodium alginate solution was mixed with a sequence of lithium chloride solutions of different concentrations. 

This vibration system involves a Turbotak air-atomizer in which a pressurized air is injected to mix with the sodium alginate solution. Pressurized air forces the minute liquid droplets out through the orifice of a nozzle and is sprayed into the calcium chloride solution. When these droplets come in contact with calcium chloride solution, calcium ions diffuses into the droplets of sodium alginate, which leads to form microgel droplets. Hydrogel particles thus formed can be further reinforced by poly-L-lysine or chitosan to form a membrane on the droplets. The particle size of hydrogel beads can be obtained in the range of 5 and 15 pm by the use of air atomization technique. ... 

The rheological behavior of sodium alginate solutions depends on the concentration and the shear rate. The Newtonian behavior and pseudoplastic behavior is observed at low shear rate and high sear rate, respectively. Higher concentrated solutions exhibit pseudoplastic flow even at low shear rates. 

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