Emulsion
Emulsion Emulsion is a colloidal system in which both the dispersed phase and the dispersion medium are immiscible liquids e. g. milk, vanishing cream, butter etc. Generally two types of the emulsions are recognized. (i) Oil in water emulsion (o/w type) (Aqueous emulsion): In this, oil particles (dispersed phase) are distributed in water (dispersion medium) e.g. when a little nitrobenzene is distributed in large excess of water an emulsion of oil in water is formed. Other examples are milk, vanishing cream etc. (ii) Water in oil...
read moreProperties of Colloidal Solution
Properties of Colloidal Solutions All the properties of colloidal solutions can be grouped under three heads: 1. General Properties: General properties of colloidal solutions are given in difference between colloid and true solution. 2. Optical Properties: (i) Brownian movement: Robert Brown (1927) an English Botanist, observed that the pollen grains in aqueous suspensions were in constant motion. Similar phenomenon was, later on, found in case of colloidal solution, when observed ultra-microscopically. This continuous and rapid...
read moreTypes of Colloids
Different types of colloids are described below: Reversible or Protective Colloids: Certain substances such as gelatin, gum, starch etc. have a great affinity for the dispersion medium and easily pass into the colloidal solution. When they are coagulated, they can be easily brought back into colloidal state. Such types of the colloids are known as Reversible Colloids. Thus, “The substances which have great affinity for the dispersion medium and even after coagulation they can be directly converted into colloidal state, are known as...
read morePurification of Colloidal Solution
Various techniques for purification of colloidal solution are as follows: 1. By Dialysis: It is done by dialysis. Dialysis is the process which is used for the separation of crystalloids from a colloid by filtration or diffusion through parchment paper or animal membrane. The apparatus employed for this purpose is called dialyser. This process is based on the fact that membranes contain very small pores through which only dissolved molecules and ions of the true solution can pass readily. The Graham dialyser consists of a hollow cylinder...
read moreColloidal Solution
In Colloidal Solution particles of the substance are in the colloidal state . It is a heterogeneous system consisting of two phases (i) Dispersed phase and (ii) Dispersion medium. Dispersed phase + Dispersion medium = Dispersed system (Colloidal solution) If the dispersion medium is water, the colloidal solutions are called hydrosols or simply sols. If alcohol or benzene is the dispersion medium, it is called alcosol or benzosol etc. Hence the colloidal solution may be defined as “The solution in which a certain substance is...
read moreColloidal state
Thomas Graham (1861) classified all the soluble substances into two following classes: 1. Crystalloids: The substances, aqueous solution of which can readily pass through vegetable and animal membranes such as inorganic salts, acids, bases, urea, sugar etc. are called crystalloids. 2. Colloids: The substances, aqueous solution of which can not pass through vegetable and animal membranes such as gelatin, starch, proteins etc. are called colloids. The term colloid is derived from Greek word kolla meaning glue-like. This view of Graham has...
read moreMechanism of Enzyme Action
Mechanism of enzyme action are as follows: 1. Lock and key model: 2. Kinetics of enzyme catalysis: According to Michaelis-Menten the enzyme catalysed reaction occurs as follows: The origin of catalase is blood, plant juice etc. Lactic bacili present in curd catalyzes the fermentation of milk. The enzyme lipase catalyzes the fermentation of sugar to produce glycerol. Digestion of food is a very complicated process. But enzymes such as pepsin and ptyalin (origin—saliva) in gastric juice work...
read moreTheory of Catalysis
The following theories are proposed to explain the mechanism of catalysis: (i) Intermediate compound formulation theory: According to this theory one of the reactants combines with catalyst to form intermediate product, which carries out the reaction, E.g. where A and B are reactants, C is the catalyst and AC is the intermediate product. (ii) Adsorption theory: According to this theory, reactants are adsorbed on the surface of the catalyst and form a film. Due to high...
read moreCharacteristics of Catalysts
Characteristics of Catalysts are as follows: 1. The catalyst remains unchanged (in mass and chemical composition ) in the reaction (Activity of catalyst.) 2. A small quantity of the catalyst is required. e.g. One mole of colloid Pt catalyses 3. The catalyst does not change the equilibrium constant. But the equilibrium approaches earlier. 4. Specificity of Catalyst: The catalyst is specific in nature. It means by the change of catalyst, nature of the products changes or specific catalyst for a specific reaction. Or 5....
read moreTypes of catalysts
Types of catalysts are listed below: (i) Positive catalysts: A catalyst which increases the rate of reaction is called positive catalyst. Such catalyst decreases activation energy by accepting a smaller path, so rate of reaction is increased. E.g. (ii) Negative catalysts (Inhibitors): A catalyst which decreases or retards the rate of reaction is called negative catalysts. It is because a -ve catalyst increase activation energy by taking a longer alternative path. E.g. (1) (2) T.E.L (Tetra...
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