Ring methods

Compared with atactic polypropylene it has a lower softening point (less than 100°C compared with 154°C when assessed by ball and ring methods), has better resistance to subzero temperatures and is completely soluble in aliphatic hydrocarbons. The molecular mass of atactic polybut-l-ene is about twice that of an atactic polypropylene of similar melt viscosity. 

Fig. 8.106 Loading-ring method of stressing a specimen (after Rating and Rinebold" )...

FIG. 1 Influence of pH on the surface tension of some alkyl ether carboxylic acids. (Concentration 1 g/1, Ring method.) (From Ref. 57.)... 

The CMC of commercial AOS and other surfactants at 40°C has been determined by Gafa and Lattanzi [6] who plotted the surface tension of aqueous surfactant solutions against concentration. The surface tensions were determined with the ring method according to du Nouy. Table 5 gives their CMC values in mmol/L and the surface tension at the CMC in mN/m. Table 5 also contains CMC values of isomerically pure sodium alkyl sulfates, sodium alkylbenzene-sulfonates, sodium hydroxyalkanesulfonate, and sodium alkenesulfonates at 40°C, taken from the literature [39 and references cited therein]. 

Compound Si-O (A) both ring types Si-O-Si n Si404 rings Si-O-Si (°) Si30j/Si404 rings Method Reference... 

For a completely symmetrical curve, the end-point can be easily established as the inflection point through which a tangent can be drawn here for convenience the "rings method (Fig. 2.23) can be used, where the inflection point is obtained by intersection of the titration curve with the line joining centres of fitting circles (marked on a thin sheet of transparant plastic see ref. 61). 

If the operating temperature of reaction 3.10 can be reduced and that of reaction 3.12 can be raised, reactions 3.10 and 3.12 can occur in the same reactor, and as a result, the time and cost of the process can be reduced. To integrate the reactions in one reactor, HyPr-RING method introduced C02 absorption reaction into the reaction system as shown in Equa-... 

HyPr-RING method was proposed in 1998 in 2000, a project started in Japan to develop this method to a commercial process. Figure 3.14 shows the concept of FlyPr-RING process. Two chemical loops are included in this process. The first chemical loop is the water cycle. 

Several new concepts under development for hydrogen production from coal were also described. The HyPr-RING method combines coal gasification, C02 separation, and water-gas shift reaction in a gasifier to produce hydrogen. 

Ball and ring method, 10 387 Ball clay, 6V686 for ceramics, 6 688... 

There are numerous other methods for measuring surface tension that we do not discuss here. These include (a) the measurement of the maximum pressure beyond which an inert gas bubble formed at the tip of a capillary immersed in a liquid breaks away from the tip (the so-called maximum bubble-pressure method) (b) the so-called drop-weight method, in which drops of a liquid (in a gas or in another liquid) formed at the tip of a capillary are collected and weighed and (c) the ring method, in which the force required to detach a ring or a loop of wire is measured. In all these cases, the measured quantities can be related to the surface tension of the liquid through simple equations. The basic concepts involved in these methods do not differ significantly from what we cover in this chapter. The experimental details may be obtained from Adamson (1990). 

Several other methods for determining 7 —notably, the maximum bubble pressure, the drop weight, and the DuNouy ring methods (see Section 6.2) —all involve measurements on surfaces with axial symmetry. Although the Bashforth-Adams tables are pertinent to all of these, the data are generally tabulated in more practical forms that deemphasize the surface profile. 

Sharma, R. R. 1963. Determination of surface tension of milk by the drop method and the ring method. Ind. J. Dairy Sci. 16, 101-108. 

Ibid., Measurement of Droplet Size by the Diffraction Ring Method, 3-18, July 27,... 

Interface by the du Noiiy Ring Method Basic Protocol 2 Dynamic Interfacial Tension Determination by the Drop D3.6.5... 

This unit will introduce two fundamental protocols—the Wilhelmy plate method (see Basic Protocol 1 and Alternate Protocol 1) and the du Noiiy ring method (see Alternate Protocol 2)—that can be used to determine static interfacial tension (Dukhin et al., 1995). Since the two methods use the same experimental setup, they will be discussed together. Two advanced protocols that have the capability to determine dynamic interfacial tension—the drop volume technique (see Basic Protocol 2) and the drop shape method (see Alternate Protocol 3)—will also be presented. The basic principles of each of these techniques will be briefly outlined in the Background Information. Critical Parameters as well as Time Considerations for the different tests will be discussed. References and Internet Resources are listed to provide a more in-depth understanding of each of these techniques and allow the reader to contact commercial vendors to obtain information about costs and availability of surface science instrumentation. 

The choice between the static methods (Wilhelmy plate method and the du Noiiy ring method) should primarily be based on the properties of the system being studied, in particular, the surfactant. As mentioned in UNITD3.5, the transport of surfactant molecules from the bulk to the surface requires a finite amount of time. Since static interfacial tension measurements do not yield information about the true age of the interface, it is conceivable that the measured interfacial tension values may not correspond to equilibrium interfacial tension values (i.e., the exchange of molecules between the bulk and the interface has not yet reached full equilibrium and the interfacial tension values are therefore not static). If the surfactant used in the experiment adsorbs within a few seconds, which is the case for small-molecule surfactants, then both the Wilhelmy plate method and the du Noiiy ring method are adequate. If the adsorption of a surfactant requires more time to reach full equilibrium, then the measurement should not be conducted until the interfacial tension values have stabilized. Since interfacial tension values are continuously displayed with... 

Figure D3.6.1 General principle of direct force-transducer-based tensiometers (Wilhelmy plate and/or du Nouy ring method). I/O is input/output.

The basic setup to determine static interfacial tension based on either the Wilhelmy plate method or the du Noiiy ring method (see Alternate Protocol 2) is shown in Figure D3.6.1. It consists of a force (or pressure) transducer mounted in the top of the tensiometer. A small platinum (Wilhelmy) plate or (du Noiiy) ring can be hooked into the force transducer. The sample container, which in most cases is a simple glass beaker, is located on a pedestal beneath the plate/ring setup. The height of the pedestal can be manually or automatically increased or decreased so that the location of the interface of the fluid sample relative to the ring or plate can be adjusted. The tensiometer should preferably rest on vibration dampers so that external vibrations do not affect the sensitive force transducer. The force transducer and motor are connected to an input/output control box that can be used to transmit the recorded interfacial tension data to an external input device such as a monitor, printer, or computer. The steps outlined below describe measurement at a liquid/gas interface. For a liquid/liquid interface, see the modifications outlined in Alternate Protocol 1. Other variations of the standard Wilhelmy plate method exist (e.g., the inclined plate method), which can also be used to determine static interfacial tension values (see Table D3.6.1). 

STATIC INTERFACIAL TENSION DETERMINATION AT A LIQUID/GAS INTERFACE BY THE DU NOUY RING METHOD... 

---