The following are summaries of seven of the papers presented at a Meeting of the Analytical Division held on July 16th-I7th, 1990, in ICI C and P Ltd., Runcorn, Cheshire.

An improved system for the phase-titration determination of kerosine adulteration in petrol has been developed. Calibration graphs are linear and are therefore especially efficacious for field applications. The range of kerosine adulteration covered (0-20% v/v) represents the extremes of adulteration found in the field.The method shows no significant dependence on temperature.

2895One reaction gave 60.0/40.0 for PrOz-do-/PrOz-dl by NMR and 60.4139.6 from microwave (MW) transitions. The second reaction gave 46.3153.7 by NMR and 46.21533 by MW. Five MW transitions2' were used; the precision of the MW and NMR ratios were similar.MW spectroscopy was employed to determine the relative amounts of EtOz-do, -d2. and -d4. The intensities of five microwave transitions (lo6,, and 1311,3 -1312.2 for EtOz-do; 139,4 -1310,3 and,l4,,,, -1411,3 for EtOz-d,; 138,5 -139,4 for EtOz-d,) were used following procedures previously worked Because of the spectral complexity and the slow decomposition of EtOz in the MW cell, the uncertainties cannot be further reduced without considerable effort.Overall yields were determined by manometric methods. In order to remove most of the acetaldehyde from the ozonides, the mixture was distilled from a -78 "C trap for -1 h. The NMR indicated that the acetaldehyde was reduced to about 5% or less. Some ozonide may also have been lost during the long distillation, but their overall yields still ranged from 70% to 85%. No systematic differences were evident between runs at low and high acetaldehyde concentrations.

No abstract

Second-order rate coefficients for the reactions of acetonitrile solutions of tetra-n-butylammonium benzenesulphonate and seven melaand para-substituted derivatives with methyl perchlorate, a t 0.3", lead to a Hammett p value (-1.1 0 f 0.04) essentially identical to those previously reported for reactions with other powerful methylating agents. When silver ion is substituted for tetra-n-butylammonium ion, the second-order rate coefficients become concentration dependent and the fall off with increasing salt concentration can be rationalised on the basis of only free anions being reactive. The calculated degrees of dissociation are applied to the previously studied silver-ion assisted reaction of silver toluene-p-sulphonate with methyl iodide. ARENESULPHONATE ions react with powerful alkylatingagents to yield the alkyl arene~ulphonate.~ For methylation the mechanism is believed to be SN2 in ~h a r a c t e r . ~-~ Studies of the reactions of acetonitrile solutions of ringsubstituted benzenesulphonate ions, supplied as the tetra-n-butylammonium salts, with methyl trifluoro-methane~ulphonate,~ the methyl iodide-silver ion comp l e ~, ~ and the trimethyloxonium ion have been extended to the somewhat less reactive6 methyl perchlorate. For reaction with the toluene-@-sulphonate ion, a study has been made of the concentration dependence of the second-order rate coefficient when silver ion is substituted for the tetra-n-butylammonium ion. The results from this study are applied to data available for the reaction of silver toluene-P-sulphonate with methyl iodide. EXPERIMENTAL Acetonitrile (Mallinckrodt ; Nanograde) was purified and the tetra-n-butylammonium arenesulphonates prepared as described previously. Silver toluene-p-sulphonate (Eastman) was dried overnight at 120", immediately prior to preparation (at 0.0') of a 0 . 2 ~ solution in acetonitrile. Concentrated stock solutions of methyl perchlorate in hexane, dioxan, or benzene were prepared by the reaction of silver perchlorate with an appropriate methyl iodide soluti0n.~9 Silver iodide was removed by filtration and the exact concentration of methyl perchlorate determined by addition of 1 .OO in1 to methanol (10 ml) and, after complete methanolysis (cu. 3 h), addition of acetone (20 ml) and titration against a standardized solution of NaOMe in MeOH to a Resorcinol Blue (Lacmoid) endpoint. The absence of contaminant acid was shown by addition of the stock solution (1.00 ml) to acetone (10 ml) saturated with LiCl(MeOC10, + LiC1+ MeCl + LiClO,) and titration as above; solutions usecl in