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level: level 6

Questions and Answers List

level questions: level 6

QuestionAnswer
1 Both O/W and W/O microemulsions may be formed spontaneously by agitating the oil and water phases with carefully selected surfactant such as __ 2 HLB range of __1) 1 Polysorbate 60 2 Polysorbate 80 2) 15-18
Emulsion is considered physically unstable if1. The internal or dispersed phase upon standing tends to FORM AGGREGATES OR GLOBULES 2. Large globules or aggregates of globules RISE to the top or FALL to the bottom of the emulsion 3. If all or part of the liquid of the internal phase becomes “unemulsified” and forms a distinct layer on the top or bottom of the emulsion as result of the COALESCING of the globules of the internal phase
A stable emulsion is characterized by the following1. NO flocculation and creaming 2. NO coalescence of globules & separation of the layers 3. NO deterioration due to microorganisms 4. Maintenance of elegance with respect to appearance, odor, color and consistency
is the joining together of globules to form large clumps or floccules which rise or settle in the emulsion more rapidly than do the individual particlesFlocculation
is the rising (upward creaming) or settling (downward creaming) of globules or floccules to form a concentrated layer at the surface or to the bottom of the emulsionCreaming
coalescence of globules and the subsequent breaking of an emulsion are irreversible processesCoalescence & breaking
1 Molds, yeast and bacteria may bring about decomposition and contamination of the emulsion. 2 Preservatives should be more __1 Deteriation by Microorganism 2 fungistatic than bacteriostatic
1 Light and rancidity affect the color and the odor of oils and may destroy their vitamin content. 2 Result in the coarseness and breaking of an emulsion.1 Miscellaneous Physical & Chemical Change 2 Freezing and thawing and high temperature
is taking up of a certain amount of liquid WITHOUT A MEASURABLE INCREASE by a gel with an increase volumeImbibition
is the taking up of a liquid by a gel with an INCREASE IN VOLUMESwelling
is when the interaction between particles of the dispersed phase becomes so great than on standing, the dispersing medium is SQUEEZED OUT IN DROPLETS AND THE GEL SHRINKS. a form of instability in aqueous and nonaqueous gelsSyneresis
is a reversible gel-sol formation with no change in volume or temperature-a type of non-Newtonian flow.Thixotrophy
is formed when the liquid is removed from a gel and only the framewok remains. Examples: gelatin sheet, tragacanth ribbons and acacia tearsXerogel