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Until now, the recommended procedure for measuring hydrolyzable tannins has been to mix the reagent and sample, subject the mixture to a certain amount of chill, allow the reaction to continue for some time at a higher temperature and then measure the absorbance of the colored solution. The effect of different chill conditions has been studied by many workers but the effect of conditions after the chill period has not been studied. In this work, the effects of changing certain reaction variables during the increased temperature time period were examined and it was found that small changes in the reaction conditions resulted in large changes in the reaction process. Additionally, the behavior of the reaction depended on the variety of plant from which the hydrolyzable tannins were extracted and the time of the season when the leaves were collected. It is recommended that no chill be used in the colorimetric procedure but, instead, the following procedure should be used: extract the plant material with 70% acetone and take 1 ml of the extract plus 5 ml of 2.5% potassium iodate and place in a test-tube. Vortex mix the mixture and immediately place the test-tube in a 25 °C water bath. When the optimum length of time has passed (which should be determined for each type of plant material and must be precisely measured), remove the sample from the water-bath and measure the absorbance at 550 nm.

A procedure for the determination of iodide in charcoals impregnated with potassium iodide is described. An aqueous extract is prepared and the iodide ion concentration in this extract (up to 4 × 10–3 mol dm–3) is determined by injection into a water stream that is merged with an aqueous solution containing potassium iodate and sulfuric acid, followed by absorptiometric measurement at 460 nm. The analysis is simple and rapid, with a limit of detection of 6 × 10–5 mol dm–3 iodide and a relative standard deviation (n= 10) of 1.2% for 1 × 10–3 mol dm–3 iodide. The procedure was used to measure the levels and the distribution of potassium iodide in impregnated charcoals. The flow method is discussed with reference to the chemistry of elementary iodine in aqueous solution.

Two simple and accurate methods are described for the determination of clindamycin hydrochloride. The spectrophotometric method involves the oxidation of the sulfur atom in this drug with potassium iodate in acidic medium with the liberation of iodine and subsequent extraction with cyclohexane followed by measuring the absorbance at 520 nm. The titrimetric method involves direct titration of the drug with N-bromosuccinimide. The relative standard deviation for both methods was less than 1%. The proposed methods were applied to the determination of the drug in pure and capsule forms.

Concentrated hydrochloric acid is added to samples of natural waters containing 2 × 10–7–5 × 10–5M iodine and the solutions are then oxidised with hydrogen peroxide on a boiling water-bath. They are then reduced with sodium sulphite, which is subsequently removed by bubbling a stream of inert gas through the solution. All of the inorganic iodine, now present in the solution in the –1 oxidation state, can be titrated spectrophotometrically with standard potassium iodate solution, following a method previously described in which interferences from oxidants and reductants are eliminated.

The misuse of sulphur-containing organophosphorus insecticides results in many instances of poisoning. This paper describes a spray reagent for their detection in biological materials by thin-layer chromatography. Sulphur-containing organophosphorus insecticides react with acidified potassium iodate liberating free iodine, which in turn reacts with starch solution to give a blue colour. In alkaline media the colour is intensified and consequently the sensitivity of detection increases. There is no interference from other organochloro insecticides or even carbamate insecticides or from the constituents of visceral extracts (amino acids, peptides, proteins, etc). The limit of detection is ca. 1 µg.

A flow injection amperometric method is recommended for the iodimetric determination of sulphite. Both the formation of iodine and its reaction with sulphite are carried out on-line in a single channel manifold consisting typically of 3 m of 0.71 mm bore transmission tubing. Iodine is formed reproducibly in the reverse FIA manner in an injected bolus of dilute acid using a slightly alkaline potassium iodate eluent containing an excess of potassium iodide, and is monitored at a glassy carbon electrode held at –0.2 V vs. SCE, without interference from dissolved molecular oxygen. When acidified sulphite standards or samples are injected into the same eluent a decreased iodine signal is obtained owing to the reaction of the sulphite injected with an equivalent amount of iodine. The decrease in signal size is rectilinear with the sulphite concentration of the injected solution in the range 0.1 × 10–4–4 × 10–4M when injection is made into an eluent 3 × 10–5M in potassium iodate and 0.1 M in potassium iodide.Methods of determining sulphite in which the reaction between iodine or bromine and sulphite is carried out off-line and the excess of iodine or bromine is determined amperometrically by injecting the reacted solution into an inert iodide or bromide eluent, or in which a slightly alkaline sample solution containing iodate-iodide is injected into an acidic eluent, have also been developed.

A colorimetric method for the determination of arsenic(III) at a concentration of 0.002 mg l–1 in potable water was developed. Arsenic(III) reacts quantitatively with potassium iodate in the presence of sulphuric acid and releases an equivalent amount of iodine, which imparts a pink colour to a carbon tetrachloride extract, this colour being measured at 520 nm. The method was used to differentiate between arsenic(III) and arsenic(V). No interference from arsenic(V), chloride, fluoride or nitrate was observed. Natural water samples analysed by this technique showed trace amounts of arsenic(III).

An iodatometric method for the determination of organoisothiocyanates is described. The isothiocyanates are quantitatively converted with n-butyl-amine in dimethylformamide medium into the corresponding symmetrical NN-disubstituted thioureas, which are titrated visually or potentiometrically in acidic medium with potassium iodate solution. Methods have also been developed for the analysis of isothiocyanate-isocyanate and isothiocyanate-thiourea mixtures on the same sample solution. A known excess of the standard n-butylamine solution added to the mixture in dimethyl-formamide converts the isothiocyanate and isocyanate into the corresponding disubstituted thiourea and urea, respectively. Acidimetric titration of the excess of amine, and iodatometric titration of the thiourea present and formed, enable the particular mixture to be analysed for both constituents. The end-points can be detected both visually and potentiometrically. The methods described are simple, accurate, reliable and widely applicable.

The stoicheiometry of the reaction of iron(II) with chromium(VI) and the suitability of potassium dichromate as a primary standard have been examined. To differentiate the effects of possible non-stoicheiometry and impurities in the samples, several different sources of chromium(VI) and three different standardisation schemes, based on the use of arsenic trioxide, sodium oxalate and potassium iodate, have been used. It is shown that the stoicheiometry of the reactions is satisfactory and that suitable grades of potassium dichromate are excellent primary standards.

Hydrazine is known to interfere in the determination of ammonia with Nessler's reagent. A method is described in which this interference is prevented by prior oxidation with potassium iodate in acidic solution. The method can be used directly for trace amounts of ammonia, or following distillation when other interfering substances are present.

A method is described for the determination of total sulphur in limestones. The sample is mixed with tungsten trioxide and quartz flour and placed in a boat of refractory material. The boat and contents are inserted into an aluminous porcelain combustion tube maintained at a temperature of about 1200 °C in a resistance-type tube furnace. The combustion tube carries a coil of copper gauze at the outlet end to reduce sulphur trioxide. Nitrogen is used as carrier gas and the sulphur dioxide evolved is absorbed in dilute hydrochloric acid containing potassium iodide and starch as indicator, titration with standard potassium iodate solution being carried out as the analysis proceeds.