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b) the capillary pressure which is necessary for formation of the

bubble or drop, or tearing away the bubble or drop (the method of

Rebinder).
To measure the surface tension the devices such as tensiometer,
stalagmometer, dynamometer DST (ДПН) and others are used. The
most commonly used methods are Du Nouy method (the method of
ring tearing away) and stalagmometer method. In particular Du Nouy

method (the method of ring tearing away) consists in measuring the
force at the moment of ring tearing away (a loop is immersed into the
tested liquid). The tensiometer K6 (fig. 9.1) consists of base 1, leg 2,
beam 3; device scale 4 with pointer 5; wire ring (measuring element)

6; cup with the tested liquid 7; support (table) 8 and holder 9.

1 – base; 2 – leg; 3 – beam; 4 – device scale; 5 – pointer;
6 – wire ring (the measuring element); 7 – cup with the tested

liquid; 8 – support (table); 9 – holder

Figure 9.1 – Tensiometer K6

The main advantages of tensiometer K6 is its efficiency (the
measurements are quick) and that for measuring the surface tension

the insignificant volume of surfactant solution is needed. The effective
range of tensiometer K6 is from 0 to 90 mN/m. Tensiometer K6

is made by German company Kruss.

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