The formation of foam is achieved simply by shaking the gas and liquid together or by bubbling the gas through a sintered glass disc into the liquid.When pure liquids re used the bubbles which form at the surface collapse rapidly.Unlike in the Breaking Of Emulsion.
Stability of foams
A stable foam is subsequently achieved when the third component, popularly referred to as foaming agent is use in the production . Typical amongst these foaming agents includes: soaps, detergents, proteins and solid powders. In all cases the foaming agent adsorbs at the
interface and although the foaming ability depends on the surface activity of the agent, the stability of the foam is determined by the nature of the liquid film.
interface and although the foaming ability depends on the surface activity of the agent, the stability of the foam is determined by the nature of the liquid film.
The factors that determine the stability of foams depends on the following:
The rate of the drainage of the liquid film particularly in the early stages, and these depends on:
1. Bulk viscosities of the liquid film
2. The ability of the film
These properties determine how much drainage must occur before the film is so weak that it raptures. In some cases, the film is so weak that is raptures. In some cases the film may be as thin as about 50Å but may be raptured by molecular forces. As considerable drainage
occurs in foams formed by common soaps and detergent these are not very stable foams. As compared to emulsions protein and solid powders from quite rigid films and the foams owe their stability to the mechanical strength of these films.
occurs in foams formed by common soaps and detergent these are not very stable foams. As compared to emulsions protein and solid powders from quite rigid films and the foams owe their stability to the mechanical strength of these films.
Breaking down of foam
The breakdown of foams maybe achieved by various methods practically, depending on the characteristics/ properties of the particular systems. The method used commercially involves spraying with organic compounds such as n-octanol which as a result of their greater surface
activity ,displaces the foaming agent from the surface leaving a film without the requisite properties to resist rapture. Also, foaming can be prevented by the addition of a suitable agent to the liquid phase e.g: silicones are now widely used as a foam inhibitor. The control of foam formation is of great importance in a number of technical processes.
activity ,displaces the foaming agent from the surface leaving a film without the requisite properties to resist rapture. Also, foaming can be prevented by the addition of a suitable agent to the liquid phase e.g: silicones are now widely used as a foam inhibitor. The control of foam formation is of great importance in a number of technical processes.
The significance of foams
The aspect of foams with industrial application is the frot flotation process for the separation of minerals during beneficiation. Another important type of foam is that it is used in fire fighting, particularly in oil fires according to onuchukwu, A. I et al on chemical formulation of a foam Retardant for petroleum fire (Int.conference, chemical society of Nigeria, Sept 20-24, p340, 2004). This foam is a dispersion of carbon dioxide gas in aqueous media containing a
saponin of protein as foaming agent. The foam is fairly rigid and floats over the burning petroleum liquids as a blanket preventing both the evolution ofs
saponin of protein as foaming agent. The foam is fairly rigid and floats over the burning petroleum liquids as a blanket preventing both the evolution ofs
The aspect of foams with industrial application is the frot flotation process for the separation of minerals during beneficiation. Another important type of foam is that it is
used in fire fighting, particularly in oil fires according to onuchukwu, A. I et al on chemical formulation of a foam Retardant for petroleum fire (Int.conference, chemical society of Nigeria, Sept 20-24, p340, 2004).
used in fire fighting, particularly in oil fires according to onuchukwu, A. I et al on chemical formulation of a foam Retardant for petroleum fire (Int.conference, chemical society of Nigeria, Sept 20-24, p340, 2004).
This foam is a dispersion of carbon dioxide gas in aqueous media containing a saponin of protein as foaming agent. The foam is fairly rigid and floats over the burning petroleum liquids as a blanket preventing both the evolution of inflammable vapour and ingress of oxygen of the air. There are some common examples of foams found in the home, these include: beaten egg, whipped cream, froth on beer and foam associated with domestic cleaning processes with soaps and detergents.
Ref:
1. onuchukwu, A. I et al on chemical formulation of a foam Retardant for petroleum fire (Int.conference, chemical society of Nigeria, Sept 20-24, p340, 2004
2. Science an chemistry of Surface an colloid chemistry by onuchukwu.
