A simple and rapid procedure is described for the determination of thiamine in certain pharmaceutical and cereal products; it depends on the intense yellow colour produced on treatment of the vitamin with diazotised 6-aminothymol. The solubility of the colour in alkaline media, together with lower sensitivity to interfering substances and precise experimental conditions, renders this reagent more suitable for routine work than p-aminoacetophenone. The method is applicable to materials containing upwards of 0.1 mg thiamine per g and the maximum experimental error of a single determination is 1-5 per cent.A SUITABLE rapid method was required for the routine analysis of cereal enrichment materials and pharmaceutical tablets containing between 0.5 and 3.5 per cent. of thiamine. The thiochrorne procedure is not ideally suitable for rapid control work and it was considered therefore, that a colorimetric method of assay was more likely to meet the requirements of the laboratory dealing with large numbers of routine samples.Numerous reagents have been proposed for the colorimetric determination of thiamine by diazotisation and coupling in an alkaline m e d i ~m . ~, ~~~~~~~~6Of these, p-aminoacetophenone has found the most widespread application in cereal' and pharmaceutical work,* y 9 and a procedure based on the use of this reagent was official in the United States Pharmacopoeia XII. The latter method represented a modification of that of Auerbach,lo in which toluene or xylene was used to extract the red dyestuff after coupling at an elevated temperature. Auerbach observed that a great variety of substances were capable of reducing the intensity of the colour produced, particularly at the higher temperatures employed to accelerate the coupling process. Elvidgell reported that errors as high as 13 per cent. were obtainable when the method was applied to comparatively pure solutions of thiamine, and later, Ballard and Ballard12 showed that, to obtain reproducible results, it was necessary t o work at higher levels of thiamine and to allow the colour to develop for a longer period at room temperature.

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A simple rnetliod is described for the detection and semi-quantitative estimation of fungal a-amylase activity of wheat flour. It depends on the selective inactivatioii of cereal amylases on bentonite in presence of sodium acetate and detectioi~ of the fungal amylase by il cup-plate technique with a starch agar substrate.

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When the reagent is used warm, the HMX reacts as quickly as RDX.