Destabilisation

If oil and water are mixed as an emulsion, dehydration becomes much more difficult. Emulsions can form as oil-in-water or water-in-oil if mixed production streams are subjected to severe turbulence, as might occur in front of perforations in the borehole. Emulsions can be encouraged to break (or destabilise) using chemicals, heat or just gentle agitation. Chemical destabilisation is the most common method and laboratory tests would normally be conducted to determine the most suitable combination of chemicals. 

In a gas flotation unit, air is bubbled through oily water to capture oil particles which then rise with the bubble to form a scum at the surface of the flotation unit. The scum can be removed by rotating paddles. Chemicals are often added to destabilise the inlet stream and enhance performance. 

The viscosity of the latex can also be dependent on pH. In the case of some latices, lowering the pH with a weak acid such as glycine is an effective method for raising the viscosity without destabilising the system. Latices made with poly(vinyl alcohol) as the primary emulsifier can be thickened by increasing the pH with a strong alkaU. 

In addition to reproductive effects, fish exposed to endocrine disrupters may have a decreased response to stress or decreased growth and metabolism which can affect their ability to survive, or to defend themselves against predators. All of these factors can affect the ability of the species to survive and to reproduce itself in sufficient numbers to maintain the stocks on which our commercial and sport fisheries are based. Not all fish species will be equally susceptible to the effects of endocrine disrupters. Selective sensitivity to such effects, especially those affecting reproduction, may well lead to major changes in the flora and fauna of some of our major aquatic ecosystems as the balance between fish, mammals, invertebrates and plants, and between predators and prey, is destabilised... 

Figure 4.6 is interesting because it shows that for the best refining performance we need both a long zone and an impurity that is relatively insoluble in the solid (low k). Unfortunately long liquid zones can be destabilised by convection, and impurities with a low k do not come to order Commercial zone refining processes may therefore involve a large number of passes done one after the other (Fig. 4.7). This obviously adds a lot to the cost of the pure material, but the process can be speeded up considerably by using the multi-heater arrangement shown in Fig. 4.8.

In suspension processes the fate of the continuous liquid phase and the associated control of the stabilisation and destabilisation of the system are the most important considerations. Many polymers occur in latex form, i.e. as polymer particles of diameter of the order of 1 p.m suspended in a liquid, usually aqueous, medium. Such latices are widely used to produce latex foams, elastic thread, dipped latex rubber goods, emulsion paints and paper additives. In the manufacture and use of such products it is important that premature destabilisation of the latex does not occur but that such destabilisation occurs in a controlled and appropriate manner at the relevant stage in processing. Such control of stability is based on the general precepts of colloid science. As with products from solvent processes diffusion distances for the liquid phase must be kept short furthermore, care has to be taken that the drying rates are not such that a skin of very low permeability is formed whilst there remains undesirable liquid in the mass of the polymer. For most applications it is desirable that destabilisation leads to a coherent film (or spongy mass in the case of foams) of polymers. To achieve this the of the latex compound should not be above ambient temperature so that at such temperatures intermolecular diffusion of the polymer molecules can occur. 

In latex technology, concentrated latex is first blended with the different additives required. To prevent premature destabilisation the powders are added as dispersions and non-aqueous liquids are generally added as emulsions. Care must be taken to avoid destabilisation, which can be brought about in different ways such as... 

The relative stereochemistry of hyperaspine (1) was determined by 2D NMR and MS methods. It has a m-fused bicyclic conformation 82 (01TL4621). The tram-fused one is disfavored by an axial pentyl group at C(8) and by a destabilising dipole-dipole interaction between the N and O atoms, which does not exist in the alternative cis conformation. 

In eq. (1) the ETT order parameter z = s(p-Pc) measures, in a convenient direction, the chemical potential from that corresponding to the ETT. From the values given in Table I for the above s and q, we readily see that the occurrence of the ETTs discussed in this paper always implies an increase of the alloy free energy. Thus, CuPt random alloys, that just below and above the equiatomic concentration present both the relevant ETT s, are less stable than CuPd or AgPd and, thus more likely to be destabilised. Moreover, the proximity to both the critical concentrations implies large contributions to the BSE from the X and L points. Now, the concentration wave susceptibility, Xcc(q). as observed by Gyorffy and Stocks, is proportional to... 

The particles therefore lose their charge. Since the charge provides the colloidal stability, the colloidal paint destabilises and deposits on the nearest surface, the car body. Primer coatings 12-35 /im thick are applied according to primer type. Each particle also contains a crosslinker for the resin, usually a blocked isocyanate. After rinsing, the primed article is passed into a hot... 

Here, a change in the aromatic —S02 conjugation at the anion radical stage should destabilise differently the C—S bonds. Unfortunately, no kinetic data on the rate of cleavage of the different sulphonic (hindered or not) anion radicals are available for the moment. 

A non-adsorbing polymer in solution can also destabilise a dispersion through a mechanism called depletion flocculation. When polymer molecules do not interact favourably with the particle surfaces from an enthal-pic perspective, they are repelled from the surface regions due to entropic reasons. A depletion zone around the particles is created which has a lower average polymer concentration than the bulk solution. The osmotic... 

Depending on the quantity of ammonia, it stabilises or destabilises ammonium nitrate. 

The same goes for propane and butane. Nitrogen oxide, hydrogen halides, and vinyl bromide stabilise acetylene, but sulphur dioxide destabilise it. 

Nitroaniline is stable when it is pure. When it is added to another compound it is dangerously destabilised. This is what happens every time it is involved in a chemical reaction. 

The interaction between nitromethane, the etherate of boron trifluoride and silver oxide gives rise to an extremely dangerous reaction. However, it is difficult to interpret it. Can it be explained by the unstable property of silver tetrafluoroborate or the destabilising effect of boron trifluoride on nitromethane ... 

Sulphuric acid at 93% was added to p-nitrotoluene. The temperature reached 160°C due to a failure of the thermal control system. The sulphonic acid formed decomposed violently at this temperature. The post-accident investigation showed that the decomposition started between 160 and 190 C. In fourteen minutes the temperature rose to 190-224°C and in one minute and thirty seconds to 224-270°C. A large volume of gas was then released during the eruption. The phenomena caused by the decomposition of nitrated derivatives in the presence of sulphuric acid will be addressed several times. What these incidents have in common is the formation of large carbonised volumes. This phenomenon is common with sulphonic acids. The nitro group role is to destabilise intermediate compounds and final compounds and to generate... 

This section is mainly concerned with reactions that involve nitric acid, of which behaviour is even more difficult to interpret. Indeed, nitric acid is not only a strong oxidant but also a nitrating agent,especially when it is combined with sulphuric acid. With nitrated derivatives it can also be destabilising due to its acidic property, which faciiitates the compounds decomposition. Since most reactions give rise to a detonation it is even more difficult to interpret the accidents. 

When heating a mixture of diethyl hydrogenphosphite and p-nitrophenol in the absence of a solvent, this caused the medium to detonate. This accident could have been caused by the destabilisation of the nitrated derivative by acid. 

Martin c.s. (43) have pointed to the remarkable linear relation of the values of both processes, measured with a great variety of R. This indicates the relative abilities of various substituents to stabilise Mn(ll) or Mn(lV) with respect to Mn(IIl) substituents which stabilise Mn(lV) destabilise Mn(ll) and vice versa. 

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