ANALYTICAL CHEMISTRY, VOL. 51, NO. 5, APRIL 1979
Methods for measuring viscosity of motor oils a t low and high temperatures were reviewed in a paper by Corringer (170)who concluded that a method analogous to the cold cranking simulator was needed to simulate the conditions of temperature, pressure, and shear under which engine oils operate to evaluate high temperature viscosity. Rosemberg (690)and Robin and Briant (680)also studied viscosity of Newtonian and non-Newtonian engine oils at high shear rates. Rosemberg used a rotary viscometer while Robin and Briant used a capillary viscometer. Johnson and O’Shaughnessy (370)measured the apparent viscosity of polymer thickened commercial and experimental multigrade motor oils in the Instron Capillary Rheometer a t temperatures from 100-320 O F (37.8-160 OC). Since they found that all the VI improvers showed strong temporary shear a t low temperatures, but differed widely in temporary shear a t high temperatures, it was concluded that a high temperature test at a high shear rate would be a better predictor of engine performance than a low-shear test. The absolute viscosity and density characteristics of several lubricant base stocks a t elevated pressures and temperatures were determined in a falling weight viscometer by Brooks and Hopkins (130). Their paper included computer generated equations of viscosity, density, and pressure coefficient of viscosity as functions of pressure for each fluid. Woodle (930)presented a paper which described procedures for performing fast viscosity-temperature and viscosity-blending calculations on lubricating oils of 2.0 cSt or higher viscosity using a simple electronic calculator with natural logarithm functions. A fluorometric method for estimating the detergency of cutting fluid emulsions was developed by Kas‘yan and Volnyanskaya (410). The measurement of thermal conductivity of lubricating oils was discussed in a paper by Agnesi et al. ( 2 0 ) . Included was a discussion on the relation of thermal conductivity to heat transfer coefficients. Krawetz e t al. ( 4 6 0 ) described methods for determining the rates of linear flame propagation of lubricants and ignition of organic liquids by hot surfaces. Ahlborn (30)investigated the use of ambient pressure measurements in an evaporation test cell as a predictive evaporation rate test and found good agreement with lubricant weight loss measurements at high vacuum. Greases. The use of differential scanning calorimetry for characterizing numerous properties of oils and greases was discussed in papers by Blaine (80)and Lovasz (530). Among the properties covered were temperature use limits, wax content, soap content, cloud point, pour point, oxidation stability, and boiling range. The thermal properties of alkaline earth soaps of hydroxystearic acids were studied by Buyanova e t al. (140)using differential thermal analysis (DTA) and polarizing microscopy. DTA was also used by Wochnowski and Freitag ( 9 2 0 )to study lithium stearate as a model soap in decalin and tetralin solutions. Wilkowa (910)performed analysis of greases by a combination of dialysis, IR, GC, and flame photometry techniques. Sesulka et al. (760)determined metals in greases by AAS and found that a modified extraction method was as sensitive as mineralization methods. In studying structure and properties of greases using dielectric measurements Perekrestova et al. (670)found that the temperatures of discontinuous increases in dielectric permeability were the limiting temperatures for use of the greases. A laboratory study of the thermal conductivity of greases made by a regular-regime bicalorimeter method was described in a paper by Tambieva ( 8 4 0 ) .
Wax J. E. Tackett, Jr. Marathon Oil Company, Littleton, Colorado
Two instruments for determining paraffin wax content in petroleum hydrocarbon mixtures were described by Harrison et al. (6E, 7E). One is based on density, viscosity, and sulfur content measurements; the other uses boiling point, density, and viscosity. Martin et al. ( I I E )used NMR to determine the trace oil content of paraffin wax with an average deviation of iz0.02 70. Rozova et al. (12E) found the international method (2-bu-
219R
tanone) for determining oil in solid paraffins better than the vacuum filtration and pressure methods. T o investigate a paraffin wax odor problem, Siklos and Nagy (14E)used infrared and NMR spectrometry to detect carbonyl and hydroxyl groups as well as olefinic and aromatic hydrocarbons in residue from acetone extracts of molecular sieve retained wax components. The chemical compositions of impurities in liquid paraffins separated from diesel fuel by urea were analyzed by Bikkulov et al. ( 2 E ) using silica gel chromatography and mass spectrometry. After pretreatment of petrolatums with silver nitrate and urea silica gel columns, Langmaack and Sucker (9E) used gel permeation chromatography to fractionate the branched paraffins prior to infrared spectral characterization. Valmalle and Karleskind (18E) identified ester waxes and paraffin waxes in industrial mixtures using high temperature gas chromatography. Szergenyi and Simon (I7E)used an improved refractive index/melting point nomographic method to determine macro- and microcrystalline wax average molecular weights with an accuracy of h4% based on gas chromatography, mass spectrometry, and osmometry. Contraction on solidification of macrocrystalline waxes was found to be 9% by a refractometric method used by Szalka (I6E). Lobachev et al. (IOE) described an automatic laboratory dilatometric instrument for measuring melting points of paraffins and petroleum products containing more than 20% paraffins. X-ray diffraction patterns for paraffin. microcrystalline waxes, and polyethylene were determined by -Junichi (8E). Ryabova and Vinnikova ( I 3 E ) reported the chemical composition and physical properties of waxes obtained by solvent refining of deasphaltizates from Western Siberian petroleums. Microcrystalline waxes separated from crude oil tank bottoms by solvent precipitation were compared with waxes separated by distillation by Angrawal and Anand (1E). T h e solubility of refined paraffin wax in kerosene was determined by Gudmondssoii and Bott ( 4 E )and compared with results from theoretical and empirical equations. They (5E)have also reported on factors affecting the deposition of paraffin waxes onto surfaces. Dressler and r h d e (3E)described methods for measuring alcohols, esters, carbonyl compounds, acids, and peroxides in oxidized paraffin waxes. Skachkova (15E) improved oxidized wax ester number reproducibility by using hydrochloric acid t o decompose the saponification products and titrating the carboxylic acids with alcoholic potassium hydroxide.
Catalysts J. Free1 Gulf Research & Development Co., Pittsburgh, Pennsylvania
A number of changes in emphasis are apparent this year compared to previous reviews. Less research is being published on cracking and reforming catalysts. The literature on hydrodesulfurization catalysts, on the other hand, has expanded dramatically. It is also clear that less attention is being given to some of the older areas, such as the measurement of total surface area, porosity, and diffusion; while studies employing sophisticated instrumental techniques have grown. The use of photoelectron spectroscopy is now widely reported, for example, and studies which apply several spectroscopic techniques to a single analytical problem have become much more common. Elemental Analysis. Zakharov et al. (137G)described an iodimetric titration for determining platinum in a variety of catalysts. Pt(1V) was reduced to Pt(1I) by iodine in a phosphate buffer medium (pH 6-8) which was molar in potassium iodide. The liberated iodine was titrated with sodium thiosulfate using a rotating platinum electrode to follow the reaction amperometrically. The same authors (36G, 37G) also showed that Pt(1V) can be titrated in a sulfate medium with 0.02 M thiourea, by using 3 M potassium nitrate as a supporting electrolyte. The oxidation current of the thiourea was measured, again using a rotating platinum electrode. Interferences and coefficients of variation were discussed for both titrations. Potter (96G) determined platinum and palladium in au-
