Foam height measurement

Figure 10. Foam half-life measurements of foam stability and foam height measurements of foaminess versus dilatational elasticity for aqueous foams stabilized by a-olefin sulfonates. (Reproduced from reference 22 Copyright 1986 American Chemical Society.)...

TABLE 1 Ross Miles Foam Height Measurements for 1% Active 0, Alkyldiphenyl Oxide Disulfonate in Various Solutions at 25°C... 

There are many laboratory methods for testing the relative merits of one defoamer against another. It is a simple matter to measure foam height as a function of time to compare the performance of various foam surfactants and defoamers. Unfortunately, this simplicity has led to a wide variety of methods and conditions used with no standard procedure that would make the measurement of foaminess as characteristic of a solution as its surface tension or viscosity. It has been suggested that the time an average bubble remains entrapped ia the foam is such a quantity (49), but very few workers ia the defoamer iadustry have adopted this proposal. Ia practice, a wide variety of methods are used that geaerally fall iato oae of five maia categories ... 

Finding F Either Eq. (22-45) or Eq. (22-46) can be used to find the surface excess indirectly from experimental measurements. To assure a close approach to operation as a single theoretical stage, coalescence in the rising foam should be minimized by maintaining a proper gas rate and a low foam height [Brunner and Lemhch, Ind. Eng. Chem. Fundam. 2, 297 (1963)]. These precautions apply particularly with Eq. (22-45). 

Foam Stability Measurements. The average lifetime (LF) is a property of bulk foams that is useful in ranking foams in order of stability. LF is defined as the area under the drainage profile divided by the initial foam height The apparatus used to determine these drainage profiles is shown in Fig. 9. 

The foaming capability and foam stability obtained from sparkling wines is usually tested by a dynamic foam stability method, as discussed in Section 2.6.2. Because these foams are evanescent and not really very stable, at least compared with the foams found in other industries, dynamic rather than static foam tests are the most suitable. In one version of the dynamic foam test, the Mosalux method, the foam heights are automatically measured using infrared beams and sensors [848],... 

A measure of the effectiveness of a defoamer. First, a column of foam is generated in a foam stability apparatus and the foam height is recorded. A measured amount of defoamer is added, and the reduction in foam height over a specified time period, for example, 2 s, is noted. The knockdown capability is the reduction in foam height. This test has many variations. Sometimes referred to as initial knockdown capability . 

As seen in Figure 13, in river water from the lower regions, both SAE(9E0) and NPE(IOEO) seemed to be degraded in a relatively short period, with no difference in foam height and with little difference by CTAS. However COD(Cr) measurements showed that about 40% of the NPE(IOEO) remained undegraded after 10 days, and even over a prolonged period. 

A high pressure windowed test cell was charged with a 0.5% solution of surfactant in l.OX brine. The cell was heated to 75 C and pressurized with COj to a pressure of 2500 psig (1.7237 X 10 Pa). A 1 1 volume ratio of liquid and COj was used. The charged cell was then agitated until its contents became thoroughly mixed. As soon as the fluids became static (ca 1 min), the foam height was measured. A second measurement was made 30 minutes later. 

The viscosity of the solutions was measured using the Cannon-Fenske viscometer. The foam tests were done by the conventional cylinder shake test In which a fixed amount of the solution Is shaken vigorously for a minute and the foam height Is monitored with time. The surface pressure measurements were carried out using a conventional Langmuir trough set-up, again with a platinum plate sensor. See text for further details. 

Figure 5. Measurements of foaming ability and foam stability for samples of raw foam, and humic substances from stream, foam, and foam extract samples from Como Creek and Suwannee River. Final foam heights were recorded after 5 minutes.

Foam volume tests can be conducted with soil or without soil. One foam volume test without soil [51], called the shake foam test or inverted cylinder test, is conducted by placing a solution of a composition into a cylinder. An amount of 100 g of I.Dll) solution (0.33 g/1 concentration for an ultra formulation) is placed in a 500 ml graduated cylinder. The cylinder is shaken or inverted a fixed number of times or for a set amount of time (e.g., 40 rotations at 30 r/min). The foam height is measured in centimeters or milliliters, which are conveniently measured if graduated cylinders are used. A foam volume test with soil is conducted the same way but soil is placed into the cylinder. The soil can either be added with the solution initially or added after foam is generated. The cylinder is rotated or inverted the desired number of times and the resultant foam height is measured in milliliters or centimeters usually at least three replicas are recorded. 

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