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Fretting wear has a significant influence on wire rope fatigue life when in cyclic bending, particularly for crossed wire contacts, where the interfacial motion of the surfaces is complex and multi...

A laser induced fluorescence system has been developed to visualise the oil film thickness between the piston ring and cylinder wall of a fired gasoline engine via a small optical window mounted in the cylinder wall. A fluorescent dye was added to the lubricant in the sump to allow the lubricant to fluoresce when absorbing laser radiation. The concentration of the dye did not disturb the lubricant chemistry or its performance. Degraded engine oil samples were used to investigate the influence of lubricant quality on ring pack lubricant film thickness measurements. The results show significant differences in the lubricant film thickness profiles for the ring pack when the lubricant degrades which will affect ring pack friction and ultimately fuel economy.

Polyetherketone (PEK) is a suitable material for tribological systems that specifically require the properties of high chemical resistance, low component weight, seizure resistance under starved lubrication conditions, and operation at higher temperatures than many other engineering polymers can survive. PEK is used with a liquid lubricant at high temperatures and velocities to reduce friction and also to control unstable friction and wear, particularly in the region of the material's glass transition temperature, Tg.Intermittent and marginal lubrication using representative high-temperature synthetic lubricants was applied to high-speed, high-temperature PEK–steel sliding contacts to determine the effectiveness of lubrication under these conditions. Variations in the stability of the thin lubricant films were observed, particularly under different load conditions. Under low load conditions, the lubricant polarity and the related ability to form a film in the contact were important. Under high loa...

Advanced engineering polymers of the polyaryletherketone (PAEK) family with carbon fibre reinforcement are finding application in engineering systems as tribological bearing surfaces under severe operating conditions that cyclically move the polymer into and beyond the glass transition temperature region. To support such an application, the friction in high-speed and low-load PAEK-steel sliding contacts was investigated both unlubricated and lubricated with a trinonyl trimellitate ester, a base fluid for high temperature industrial lubricants. Four polymers in the PAEK family, PEEK, PEK, PEKEKK and PEKK, with 30 wt% of carbon fibre whiskers were tested against an AISI 4140 steel disc. When unlubricated, low friction depended upon the formation of a PAEK transfer film on the steel disc and when this became unstable in the glass transition region the friction increased to much higher levels with associated polymer surface damage. Frictional heating due to the high sliding speed dominated the differences in glass transition behaviour between the four PAEKs. When lubricated, the lubricant film controlled friction and there was no significant effect of the glass transition of any of the PAEKs. The irreversible nature of the glass transition in PAEKs in such tribological applications, due to high surface damage at high temperature, means that it is essential to ensure effective lubrication in both fluid film and boundary lubrication.

Purpose – This paper aims to establish the acid concentration of finely dispersed droplets in hydrocarbon oils. Small quantities of aqueous sulphuric acid (H2SO4) were found to be trapped within hydrocarbon shells, making them inaccessible for concentration evaluation by titration. Design/methodology/approach – Fourier transform infrared spectroscopy (FTIR) used in the attenuated total reflection mode (ATR; FTIR-ATR) was applied to study the reaction products of squalane, C30H62, and an API Group I base oil with various concentrations of aqueous H2SO4. Findings – The absorbance comparison usually used for estimating acid concentrations was found to fail when small quantities of acid are trapped in the reaction product. It was found that the peak shift and changes in absorbance found for various pure aqueous acid concentrations were useful to establish the remaining concentration of the trapped H2SO4. Originality/value – This paper fulfils the identified need to study acid dissociation-dependent peak shifts of H2SO4 to find the acid concentration of finely dispersed droplets in hydrocarbon oils.

The effect of sulphuric acid on the chemical and physical behaviour of the piston ring lubricant in a marine engine cylinder was investigated. To reveal the basic influence of H2SO4 on the lubricant film, the saturated hydrocarbon Squalane (C30H62) was chosen as a simple model oil. The interfacial tension between aqueous H2SO4 (0–98% w/w) and C30H62 was measured between −3 and 165 °C to understand droplet formation in the lubricant. Interfacial tension decreases with increasing acid concentration and is temperature dependent. The wettability of engine parts with corrosive sulphuric acid was characterised by the contact angle. The contact angle of H2SO4 (0–98% w/w) on a grey cast iron cylinder liner material (Wartsila, RT84) and a piston ring chrome-ceramic coating (Federal Mogul Goetze, CKS, o960 mm) immersed in C30H62 was measured over a temperature range from 20 to 165 °C. In general, larger contact angles were measured under higher temperature conditions and on chrome surfaces. In addition to the physical measurements, chemical reaction between H2SO4 and C30H62 was observed which influenced the interfacial tension, visual appearance, phase separation and formation of solid matter. The reaction time was found to be faster than the neutralisation times of commercially formulated lubricants. The reaction products were analysed using FTIR spectroscopy and EDX to find oxidation and sulphonation.

The potential risks of transporting, transferring and storing very large volumes of crude petroleum and also refined products is discussed together with the associated environmental issues of soil/groundwater contamination and gaseous emissions.

For a chromium-nitrided steel piston ring section sliding against an electroplated nickel matrix silicon carbide coated eutectic aluminium—silicon alloy automotive cylinder bore in a reciprocating tribometer, the ionic liquid (IL) imidazolium tetrafluoroborate has an excellent tribological performance as a lubricant additive in the presence of tritolyl phosphate (TTP). A low friction coefficient of 0.015 and a substantial tribofilm was generated. The performance of this base oil/additive combination was superior to the base oil alone or the separate additives in the base oil. The substantial improvement in tribological performance given by addition of an IL and TTP, 1 per cent by volume of each, to a group III base oil indicates a synergistic interaction between the IL and TTP. The need to understand the chemical and physical nature of the tribofilm is emphasized.

The use of imidazolium tetrafluoroborate, IMM+BF4−, and hexafluorophosphate, IMM+PF6−, ionic liquids as lubricants was investigated at 25 and 100 °C to show lower friction coefficients but higher wear rates than a reference hydrocarbon lubricant. The ionic liquids readily form tribofilms at the lower temperature but have difficulty in forming partial films at the higher temperature. Wear tracks for a Plint TE77 reciprocating ball-on-plate test using ionic liquids show smoother surfaces, with small pits developing, compared to the reference hydrocarbon lubricant test result. Similar ionic liquids not containing fluorine were found to be less effective as lubricants. Addition of ionic liquids to a base grease and a formulated high temperature grease gave surprisingly large increases in the weld load for the Four Ball extreme pressure test. Little difference between base grease and base grease+5 per cent ionic liquid was observed for the TE77 test. There was no clear indication of the effect of alkyl substituent chain length on the imidazolium cation for the Four Ball test wear scar diameter. Addition of 1 per cent tricresyl phosphate (TCP) to ionic liquids rapidly establishes a tribofilm and reduces the wear volume by 64 per cent compared to the same test for the neat ionic liquid or neat TCP. Addition of 1 per cent TCP and 1 per cent ionic liquid to a Group III base oil also establishes a substantial tribofilm and reduces wear volumes compared to the base oil with 1 per cent TCP alone or the base oil with 1 per cent ionic liquid alone. Ionic liquids show promise as neat liquid lubricants by establishing a tribolayer chemically adsorbed to the steel surfaces. They are not as effective as a reference hydrocarbon lubricant in reducing wear of those surfaces by tribocorrosion. The fluorine-free ionic liquids investigated were not as effective as those containing fluorine. The addition of ionic liquids to grease, base or fully formulated, gave a substantial improvement in performance, which indicates a synergistic interaction with the additives present in the formulated grease. There is also clear evidence of a strong synergistic effect between ionic liquids and TCP, both for the neat ionic liquids and for 1 per cent dilution of each respectively in a Group III base oil to give a thick tribofilm and substantially reduced wear in the TE77 ball-on-plate test. The nature of the synergy between ionic liquids and TCP requires further investigation.

Samples of formulated lubricant have been obtained from the top piston ring zone of a standard operating petrol test engine, the Petter W-1. ESR spectra of samples frozen immediately and also those allowed to stand at room temperature show a range of paramagnetic features, some of which interconvert with change in temperature and sample history. The ESR spectra of any organic radicals are absent but a ‘radical’ centre is identified as arising from amorphous carbon. In contrast, various metal centres are identified, Fe III high-spin centres decaying to low-spin Fe III centres. C II and Mn centres are also identified with hyperfine coupling to 14 N and to Cu II . It is argued that the hyperfine interactions from ligands to these centres may result from decomposition products of the additive pack components, for example 14 N hyperfine interaction to the Cu II from the nitrogen-functionalized dispersant and sulphur-centred ligands generated by the decomposition of the zinc dialkyl dithiophosphate antioxidant/anti-wear additives.

The continuous flow stirred tank reactor model has been applied to the analyses of lubricating oil as a major contributor to the condition monitoring of i c engines. The need for a volume correction to account for the dilution effect of added, fresh, lubricant is demonstrated for the model and then developed for two examples. It is demonstrated that application of the volume correction/dilution model allows the oil analysis data base to be transformed from relative to absolute values. The ‘absolute wear’, the ‘current wear rate’ and the ‘change in the wear rate’ can then be simply calculated at any time as a fitted, smoothed, function of the analytical parameters with sample service time, its first and second derivatives, respectively. Implications for diagnosis and prediction from the corrected data base are considered.

SYNOPSIS Vegetable oils have been introduced as alternative fuels for diesel engines because they are renewable and have less pollution effects than fossil fuels. However, in many countries, their prices are higher than the ordinary diesel fuel. Therefore, it is not economic for engine users to use the vegetable oils as alternative fuels. Another suggestion is the use of vegetable oils as an engine lubricant, which may be more economically acceptable. Nevertheless, the principal weakness of vegetable oils for lubrication has been their tendency to oxidise, giving rise to gum, varnish and sludge formation. The examination of the degradation of the vegetable oils in an engine is necessary. This paper describes a technique for accelerating oil degradation in an engine by decreasing the oil sump capacity. By this technique several vegetable oils have been tested and satisfactory results have been obtained.

The base content, total base number (TBN), has been determined for a range of petroleum products and used engine oils, by both potentiometric and conductimetric methods. Titration values depend both on the method of detection and solvent media used. A conductimetric titration method for TBN is described based upon IP 177 and 276 (ASTM D-664 and 2896) solution chemistry. The results of the conductimetric titration TBN determinations are compared with those from IP 177 and IP 276 potentiometric determinations to show that the TBN order of magnitude is IP 276 (potentiometric) > conductimetric > IP 177 (potentiometric). The conductimetric method equilibrates very rapidly and is suitable for automatic titrimeters. Results for new and used oils determined by these different titration methods are discussed. Conductimetric detection for TBN determination uses standard IP method reagents and solvents and is an alternative to the trisolvent TBN method.

The contributions to the tribological chemistry of engine lubricating oil additive pack components of detergents, dispersants and corrosion inhibitors, are discussed in terms of hydrogen bond formation, proton transfer, inverse micelle formation, aggregation, solubilization, neutralization and corrosive action.

The absolute values of total base number (TBN) were determined for several sets of both fresh and used engine oil samples. Basic and acidic compounds from these oils have been extracted into water, 7% sea water and ethanol-water (1:1, v/v) mixtures. The extracts have been determined by potentiometric titration as pH extracts, TBN (water extract) and alkalinity. The oil formulations are not resistant to the presence of water but basic additives in fresh oil are more resistant than those for used oils. The percentage of TBN extractable into water significantly increases with service life. The presence of significant amounts of water in lubricating oil is serious and should form part of any lubricant condition monitoring system. The case is argued for both the use of dehydration canisters in oil systems and for the development of a new method of water content determination for used formulated lubricating oils which is quick, accurate and suitable for automated condition monitoring systems. The pH of aqueous extracts for condition monitoring of lubricating oils is shown to be only meaningful for TBN values of 2 or less.

A possible third contribution to the elastohydrodynamic lubrication effect is proposed based upon differential diffusion of higher and lower molecular weight hydrocarbons in the tribological contact. The effects of molecular weight and structure on the physical properties of hydrocarbons show that lower molecular weight, linear hydrocarbons have lower viscosities, and therefore higher self diffusion coefficients, than higher molecular weight, extensively branched structured, hydrocarbons with higher viscosities and lower self diffusion coefficients. In an equilibrium, isotropic, situation separation of lower and higher molecular weight hydrocarbons does not occur. In the elastohydrodynamic contact, under certain rates of relative movement of the metal boundaries, a non-equilibrium, anisotropic, situation will allow the lower molecular weight hydrocarbons to preferentially diffuse forwards in the direction of movement, giving a transient enhancement of higher molecular weight hydrocarbons remaining in the contact. This will give a higher viscosity and higher viscosity-pressure coefficients in the contact generating a fluid pressure above that predicted from the bulk equilibrium physical properties of the mixed fluid. Implications for base oil formulation are discussed.

Problems of diesel fuel reduced lubricity and associated injector pump wear rates are briefly reviewed to demonstrate the need for fuel lubricity additives and measurements of their effectiveness, the HFRR method. The general pattern of wear scar reduction using the HFRR test rig plotted against lubricity additive concentration has the form of an inverse sigmoidal curve. A general model is proposed for wear reduction by diesel fuel lubricity additives against their concentration. The model proposes an equilibrium between anti-wear additives solubilised in diesel fuel and an additive film of those additives adsorbed onto a metal surface undergoing rubbing wear, leading to three regimes. First, at low concentrations the model describes an initial, incomplete coverage of the metal surface by an additive film which is insufficient to support anti-wear action. Second, further increase in additive concentration gives a nearly complete and coherent film at the metal surfaces which is then able to separate the surfaces and support anti-wear action. Third, beyond this point further increase in fuel additive concentration gives no further decrease in wear rate because the adsorbed film is complete. The model therefore describes a reverse sigmoidal dependence of the metal surface wear rate upon additive lubricity concentration. It is further proposed that the interaction between a metal surface undergoing rubbing wear and anti-wear fuel additive species is in equilibrium between multiple additive species adsorbed in a non-specific manner at the metal surface and multiple additive species in the fuel. This interaction is not specific for any lubricity additive but may occur for a mixture of additive species but to a different extent for each separate molecular species. These separate molecular additive species may be adsorbed at the metal surface to form separate and coherent homogenous domain clusters at the metal surface due to entropy effects. Therefore, mixed lubricity additive concentration will act in a colligative manner with the contributions of one additive species concentration being either more or less effective compared to another additive species but adding together to give a joint effect. Examples of the model applied to diesel fuel lubricity wear rates are given for single additives together with examples of multiple additive effects on wear rates.

Development of the ring zone sampling technique for operating internal combustion engines is described. Results show a standing ring of lubricant in the piston ring zone which is substantially degraded compared to that of the sump lubricant. Recent work shows that the degradation of a formulated lubricant can be followed by multiple sampling points in the ring pack, e.g., complementary anti-oxidant degradation/protection of base oil is demonstrated. ‘Residence times’ for lubricant in the ring zone are defined and their determination discussed. The influence of bore and ring surface finish is emphasised. Extension of the technique to differentiate between different quality of lubricants and the different conditions of first ring and the base of the crown land for a piston is described. The principal areas of detailed knowledge which are not known for piston ring lubrication and tribology are examined.Copyright © 2005 by ASME

Samples of lubricant obtained from the piston ring of a petrol engine under cold start conditions are very different from the sump lubricant condition. Samples from the first operating hour show substantial fuel and water dilution which cause precipitation of additive from the lubrication formulation with multiple phase formation. The physical performance properties of these lubricant samples are drastically changed, e.g., Base Number drops from 10 to less than 2, anti-oxidancy is reduced and viscometric properties are changed. Implications for short vehicle journeys and temperature distributions within the piston assembly are discussed.

Two studies at three sites in the UK provided confirmation that systematic positive bias in NO2 diffusion tube measurement occurred because of changes to "within-tube" chemistry, rather than eddy diffusion at the mouth of the tube. In the first study in Cambridge, UK, sampler overestimation for 1 and 2 week exposures was compared to corresponding time-averaged monitor measurements (NO-NO2-NOx, O3) and weather variables. Noninearity between sampler and monitor NO2 measurements was interpreted in terms of spatial and temporal variations in relative and absolute availability of NO, NO2 and O3 at the site. A maximum overestimation occurred for an exposure mean NO2/NOx approximately 0.5. The separate contributions of reduced NO2 photolysis and eddy diffusion were compared in Study II using samplers of two materials, acrylic and quartz, and of different lengths (40, 55, 71 and 120 mm) at three sites: Norwich background, Cambridge intermediate, London kerbside. For compared sites, NO2 measured by acrylic samplers was significantly higher than for equivalent quartz samplers. For quartz samplers [NO2]mean was only just above the monitor at Norwich and London; sampler/monitor NO2 = 1.04 (P = 0.59) and 1.01(P = 0.76), respectively. For acrylic samplers the order of [NO2]mean was 40 mm > 120 mm > 71 mm > or = 55 mm. Excepting 40 mm samplers, this accords with a chemical bias where co-diffusing NO and 03 molecules in longer tubes have more time to react to form excess NO2. Bias in 40 mm samplers is discussed. Eddy diffusion is negligible for standard samplers because [NO2]mean was equivalent for 55 mm and 71 mm acrylic samplers and close to monitor NO2 for 71 mm quartz tubes. Both studies showed that sampler accuracy was dependent on location. Significantly, overestimation was greatest (approximately 3-4 ppb) where the NO2 annual mean was approximately 20 ppb, close to the UK and EU air quality standard of 21 ppb.

Factors concerning NO2 uptake by the absorbent triethanolamine (TEA) in NO2 diffusion tubes are examined. Although the nominal freezing point of TEA is 17.9-21.2 degrees C, we show that, for a range of aqueous TEA solutions (0-20%, H2O), no freezing occurs even at -10 degrees C. Therefore NO2 collection efficiency is unlikely to be impaired by low temperature exposure. The recovery of TEA from the meshes of exposed samplers is determined as approximately 98%, even after 42 days, showing that the stability in situ of TEA is unaffected by long-term exposure. A model of a diffusion tube sampling array for simultaneous exposures, with a 0.1 m sampler spacing, shows that NO2 uptake by individual samplers is not affected by the presence of neighbouring tubes in the array. This is confirmed by sampler precision at two Cambridge sites. Four sampler preparation methods are compared for differences in NO2 uptake of exposed samplers. All methods employ TEA as absorbent, transferred by either dipping meshes in a TEA-acetone solution or pipetting aliquots of a TEA-H2O solution onto the meshes. For samplers prepared by three of the methods, no difference in NO2 uptake is found, but for samplers prepared using a 50% v/v TEA-H2O solution, a mean reduction of 18% is found. Student's t-tests show that the difference is highly significant (Por = 0.001). Reasons for the difference are discussed.

It is demonstrated that the composition of lubricating oil obtained from the top ring zone of a spark ignition, natural gas, internal combustion (i.c.) engine at top dead centre (TDC) is very much different from that of the oil in the sump. The implications of this observation for wear in the bore of i.c. engines and piston fouling are briefly discussed.

The far-UV solution spectra of cyanide (CN–), cyanate (NCO–), selenocyanate (NCSe–) and tellurocyanate (NCTe–) are reported in a range of solvents and over a wide range of temperatures. Detailed computer analysis of the absorption profiles shows several bands to be present whose solvent and temperature shifts for the first two bands are different from the third, intense, high-energy band. The band properties are analysed in terms of CTTS character for the first two bands and an intramolecular electronic transition for the third band. The nature of the electronic transitions for the NCX– series, including thiocyanate, is discussed.

Most multi‐storey car parks do not have air pollution problems. But some do, together with problems of acute traffic congestion within them and difficulties in leaving them. Traffic fumes build up and these car parks get poor reputations with their users. This paper looks at how these problems occur and what operators can do to reduce or remove them.

The intrinsic viscosities and shear dependence of viscosities of solutions of poly(ethylene oxide) in t-butyl alcohol/water mixtures were investigated. A marked minimum in intrinsic viscosity at a certain alcohol concentration has been correlated with changes in the water structure brought about by the addition of alcohol. The results are interpreted in terms of rigidity-flexibility transformations of the polymer chain. Die Grenzviskositaten und die Scherabhangigkeit der Viskositaten von Polyathylenoxid-losungen in t-Butylalkohol/Wasser-Mischungen wurden untersucht. Ein deutliches Minimum der Grenzviskositat bei einer bestimmten Alkoholkonzentration wird mit Veranderungen der Wasserstruktur in Beziehung gebracht, die durch die Zugabe des Alkohols hervorgerufen werden durch die Annahme von Anderungend in der Starrheit der polymeren Kette gedeuted.

Techniques and apparatus for extending conventional solution absorption spectrophotometry into the far uv region are discussed. The principal difficulties of spectroscopy in this region are reviewed. Applications and examples are given in inorganic, organic, and biological chemistry.

The far-ultraviolet spectra of the hydrosulphide ion in a range of red- and blue-shifting solvents shows a set of four absorption bands of differing character. The lowest energy pair, A and B, are similar to those observed for the halide ions and have high solvent sensitivities. The higher energy, higher intensity D and E bands are also similar to those found at high energies for the halides. The solvent sensitivity for the A band of HS–, relative to that for the solvated electron, is 0.85.Dissection of the energy diagram in terms of ionisation potential and ionic radius shows that the adsorption spectrum of hydrosulphide is very similar to that for bromide. On the other hand, the solvent sensitivity is close to that for chloride whilst band asymmetry parameter, ρ, and band-widths, ν½, are considerably greater than those for the halides. It is concluded that the unique character of an ion contributes to some change-transfer-to-solvent (c.t.t.s.) properties and not to others.

The far ultraviolet absorption spectra of iodide ion have been studied in a large range of solvents and over a large temperature range. These include both strong blue- and red-shifting solvents relative to water and D2O. A number of new absorption bands have been observed, in some cases down to 165 nm. The observed absorption spectra are envelopes composed of overlapping absorption bands which have been resolved, using mainly lognormal (asymmetric) band shapes, to show sets of band pairs labelled A1/A2, B1/B2etc. The first characteristic charge-transfer-to-solvent (c.t.t.s.) doublet, A1/A2, has a separation close to the doublet splitting of the 2P atomic states of the iodine radical in the gas phase. The B1B2 higher energy doublet bands have a slightly smaller separation and have c.t.t.s. character such as high solvent and temperature sensitivities. At higher energies further bands are observed. The band systems observed have been correlated on the basis of solvent shifts, doublet band splittings, oscillator strengths and temperature coefficients. The c.t.t.s. character of the higher energy bands has been evaluated and tentative assignments suggested.

A linear correlation is presented between the absorption maxima of the first absorption bands of bromide and chloride, in a wide range of solvents at 298 K and νmax for solvated iodide in the same solvents. The solvents include acetone, nitriles, phosphates, H2O, D2O and fluorinated aliphatic alcohols. The correlation between the CTTS solvent scale for iodide and the absorption maxima of the solvated electron at 298 K in 38 solvents and solvent mixtures has been extended and brought up to date. The linear correlation for iodide is of the form νmax(e–solv)=[νmax(I–solv)× 1.59–56.30]× 103 cm–1. At νmax(e–solv)= 0, νmax values of 35.41, 39.78 and 43.68 × 103 cm–1 were derived for iodide, bromide and chloride, respectively. These values are consistently higher than the ionisation potentials of the corresponding free ions. On subtraction of the ionisation potentials, an “excess energy” value of 10.57, 12.52 and 13.91 × 103 cm–1 is obtained for iodide, bromide and chloride, respectively. A plot of the “excess energy” values against the crystallographic radii of the halide ions was found to give a linear relationship. These and other results are discussed. In particular, the ability to predict νmax for the solvated electron for a solvent in which νmax for iodide is known is stressed.

The far ultraviolet solution spectroscopy of hydroxide in a range of both blue and red-shifting solvents shows the absorption to be due to a c.t.t.s. transition. Comparison with the Treinin c.t.t.s. solvent scale shows OH to have a very high solvent sensitivity which, when normalised against the solvent sensitivity of solvated electron, shows a smooth, monotonic relationship for the halides and hydroxide plotted against their ionic radii. A linear correlation between the “excess energy” terms for these ions and their hydration entropies is demonstrated.

The homoconjugation, (ArO)2H–, and heteroconjugation, Ar′O–⋯HOAr, (where Ar is aromatic) with proton transfer have been determined in acetone at 298 K. Tetra-alkylammonium phenolates were titrated with a variety of phenols to given homocomplexes and heterocomplexes. Potentiometric data give the overall equilibria constants, K0, proton-transfer constants, KPT and formation constants, Kf. Two types of heterocomplexes were studied. When ArO– is a weaker base than Ar′O–, the complexation occurs without proton transfer, as confirmed by the low K0 values for the reaction. The overall equilibrium constants, K0, are large when ArO– is a stronger base than Ar′O–, as both the equilibrium proton-transfer constant (KPT) and equilibrium formation constant (Kf) of the hydrogen bond are included in the measurement of K0=KfKPT.

The far-ultraviolet solution of very dilute thiocyanate ion in a range of solvents shows that there are at least three absorption bands labelled A, D and E. All three bands are shown to have charge-transfer-to-solvent characteristics, in contrast to some previous reports. The conflicting previous reports of the spectroscopy and photochemistry of thiocyanate ions, together with the current work, are resolved in terms of a spectroscopic transition scheme involving a forbidden transition at ca. 36 000 cm–1, which is normally extremely weak or not detectable. This transition is only detected at high concentrations of salt. The first allowed transition is expected to occur at ca. 62 000 cm–1. Within this scheme the c.t.t.s. bands occur (in aqueous solution) at 46 000 and 53 500 cm–1. A further band is observed in red-shifting solvents at ca. 57 000 cm–1. The temperature sensitivities of the three c.t.t.s. bands, relative to the solvated electron, are 0.58, 0.47 and 0.30.

Electrometric properties of the homocomplexes (CF3COO)2H– and (C6Cl5O)2H– and the heterocomplexes Me3NOH+A–, Me3NOH+AHA– and (Me3NO)2H+A–(where HA is trifluoracetic acid or pentachlorophenol) have been investigated by the electrometric titration method (e.m.f.) in acetonitrile (AN).The formation constants, Kf, of the above complexes have been determined. In the homocomplexes log Kf[(CF3COO)2H–]= 4.18 and log Kf[(C6Cl5O)2H–]= 3.5 in AN; for the heterocomplexes Me3NOH+A–, Me3NOH+AHA– and (Me3NO)2H+A–, A–= CF3COO–, log Kf= 3.92, 5.52 and 6.82, and when A–= C6Cl5O–, log Kf= 4.2, 3.87 and 5.22, respectively. The acid pKANa was found to be 13.03 for CF3COOH and 16.46 for C6Cl5OH.For hydrogen-bonded complexes a gradual change in proton activity, paH, for a series of species passes through a maximum or a sigmoidal curve when paH(CB=CHA)=f(ΔpKANa). The sigmoidal and lambda curves which are produced when the formation constant and other parameters of charged and molecular complexes are plotted against ΔpKa in water and non-aqueous solvent are discussed.

The rate constants, k, for the decomposition of ammonium trichloroacetate in acetonitrile were determined at 298 K BHCCl3COO [graphic omitted] CHCl3+ CO2+ B where B is an N-base. The first-order decarboxylation of trichloroacetic acid in the presence of N-bases is strongly dependent upon proton transfer in ([graphic omitted]) complexes.Discussion of the rate constants, k, obtained shows 3 types of complexes in the proton-transfer mechanism, i.e. a symmetrically positioned proton, and without proton transfer for 2 cases: [graphic omitted]. The sigmoidal curve of rate constants, – log k, plotted against pKANa(BH+) describes the location of the proton in the hydrogen bridge. The behaviour of (CCl3COOHR)– complexes has many similarities to the molecular complexes, CCl3COOHB, discussed above. Implications of these results for carboxylate additives in overbased lubricating oils are discussed.

The far u.v. absorption band profiles of iodide dissolved in a variety of solvents have been deconvoluted using a comprehensive computer program. Several different approaches are incorporated within the overall program, including an iterative least mean squares minimization method for a combination of linear normal (Gaussian) curves, and another similar method which uses instead a linear combination of log-normal curves. The results obtained using the separate approaches demonstrate that the absorption spectra of solvated iodide are comprised of sets of band pairs arising from the 2P3/2–2P1/2 iodide radical doublet.

This spectroscopic and thermodynamic study of aqueous dimethyl sulphoxide (DMSO) suggests that the properties of the system are dominated by direct component interaction. Maximum inter-action occurs in the region of 0.35 mole fraction (DMSO) and “enhancement of water structure” by added solute is absent, except perhaps at very low concentration, < 0.01 mole fraction. The excess enthalpy HE, is compared with literature values.

νmax and Iµmax for the n–π* transition of acetone in aqueous solution do not vary monotonically with acetone concentration. The Klotz-Worley R parameter for these solutions shows a maximum at 0.05 x2 whereas carbonyl infrared intensities are a linear function of acetone concentration. Hydrophobic hydration of acetone is proposed in the initial region with direct molecular interaction at approximately 0.20 and 0.45 x2.