14 THE ANALYST. NOTES ON THE DETECTION OF ALUM I N FLOUR AND BREAD. BY J. ALFRED WANKLYN. THE want of a method for the estimation (or even of the detection) of the sulphuric acid which forms part of the alum put into flour and bread has been felt by analysts. Owing to the existence of sulphur in gluten to the extent of about one per cent., sulphuric acid makes its appearance in the ash obtained on calcining flour and bread, and, as I have shown, the sulphuric acid of the alum is overwhelmed by tbat naturally presentTHE ANALYST.15 in the ash of flour and bread. It is, therefore, to no purpose to make estimations of the sulphuric acid in the ash of dumed bread. From some experiments recently made in my laboratory, I have been led t o seek for the sulphuric acid in the cold aqueous extract of flour. The major part of the mineral matter of flour goes into the cold aqueous extract, whilst the total weight of the extract is only some five per cent. of the flour. Before determining the sulphuric acid in the extract I coagulate the soluble gluten and remove it by filtration.