Tyndall beam

Tyndall Meter—The Tyndall meter is a device developed by Tolman and Vliet (1919) for measuring the intensity of a Tyndall beam. The apparatus is shown in Figure 54 and consists of a central cell which contains the suspension to be measured. This is illuminated by a light beam whose intensity has been standardized. This beam of light passes through the cell. The intensity of the resulting Tyndall beam in the cell is measured by means of a photoelectric meter, or an illuminometer. Several variations of the Tyndall meter are possible, as follows ... 

Hatch and Choate (1929), in studying the relationship between the strength of a Tyndall beam and parameters of particle-size, obtained the relation... 

Optical methods for measuring particle surface are widely used. They are based largely on the obscuring power of particles held in suspension, or the degree of polarization exhibited. The first-mentioned method depends upon Eq (9 23) where it- was shown that the reflection of light by a Tyndall beam is a function of particle surface. The polarization of light by small particles is a function of particle-diameter... 

Measurement of polarization of the Tyndall beam of aqueous suspensions as an aid in determining particle size. Ibid., 210 793-804. 

Relation between intensity of Tyndall beam and size of particle." J, Am. Chem. Soc., 41 575-587. 

Relation between the intensity of Tyndall beam and concentration of suspensions and smokes." Ibid., 41 300-303. 

Figure 2. Light scattering aerosol as viewed in a Tyndall beam...

Tyndall Beam Lighting. A technique of indirect lighting used to reveal normally invisible dust particles by sideways scattering of the light, as dust motes are revealed by a shaft of sunlight. 

While it is vital to identify and measure the contaminant that is being dealt with, it is also important to be able to determine the effectiveness of the control measures. Within the Inspectorate a photographic technique based upon Tyndal beam effect has been developed which allows examination of the effectiveness of ventilation plant and quicker identification of the leakages or escapes of dust or other materials which are not being adequately controlled. Some of the information obtained by this technique has a staggering effect upon some industrial users when they see for the first time that an elaborate ventilation plant in fact controls none of the dust which they are generating. 

Tyndall effect When a beam of light is passed... 

Spectroscopic examination of light scattered from a monochromatic probe beam reveals the expected Rayleigh, Mie, and/or Tyndall elastic scattering at unchanged frequency, and other weak frequencies arising from the Raman effect. Both types of scattering have appHcations to analysis. 

A colloid fog will scatter a beam of light. This is called the Tyndall Effect and can be used as a troubleshooting tool. 

Airborne particulates include dust, fume and aerosols. Many such particles are invisible to the naked eye under normal lighting but are rendered visible, by reflection, when illuminated with a strong beam of light. This is the Tyndall effect and use of a dust lamp provides a simple technique for the rapid assessment of whether a dust is present, its flow pattern, leak sources, the effects of ventilation, etc. More sophisticated approaches are needed for quantitative data. Whether personal, spot or static sampling is adopted will depend upon the nature of the information required. 

Tyndall lamp A parallel light beam pro jected onto a cloud of dust particles gen crated from a process to produce scattering of the light, allowing an assessment of the magnitude and path of the cloud. 

If a beam of light is passed through a colloidal solution, the colloidal particles will reflect or scatter the light so that the beam becomes visible when the solution is viewed from the side against a dark background. This Tyndall effect is used in the ultramicroscope. 

But the microscopic fat particles suspended in milk have an average diameter in the range 10-7 to 10-5 m, i.e. much larger than k of visible light. A beam of incident light is scattered rather than transmitted by a suspension of particles - a phenomenon known as the Tyndall effect. 

A colloid is a mixture in which the solute particle size is intermediate between a true solution and a suspension. If a light is shone through a colloid, the light beam is visible. This is the Tyndall effect. 

TYNDALL EFFECT. A phenomenon first noticed by Faraday (1857). When a powerful beam of fight is sent through a colloidal solution of... 

L. Pasteur, J. Tyndall, E. T. Chapman, P. Miquel, W. Spring, F. Schulz, etc. Air may be freed from dust particles, etc., in suspension by filtration through biscuit earthenware, asbestos, or cotton wool. When a beam of sunlight is passed through unfiltered air, it reveals a multitude of motes constantly in motion. Lucretius, in his Be natura remm (2.113, 60 b.c.), has given a very vivid description of the phenomenon. With filtered air, there is no such eflect, and J. Tyndall said that such air is optically empty. F. O. Rice showed that in a number of reactions— e.g. the oxidation of soln. of sodium arsenite or sulphite, the decomposition of hydrogen dioxide, etc.—the suspended dust in air acts as a catalytic agent. 

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