─────────┬────────────┬───────────────┬────────────────────── No. of │Total Acids │ Volatile Acids│ Fixed Organic Acids Handler. │ reckoned │ reckoned │ reckoned as Lactic. │ as Acetic. │ as Acetic. │ ─────────┼────────────┼───────────────┼────────────────────── 1 │ 0·205 │ 0·050 │ 0·232 2 │ 0·628 │ 0·237 │ 0·586 3 │ .. │ 0·372 │ .. 4 │ 0·688 │ 0·426 │ 0·393 5 │ 0·569 │ 0·432 │ 0·206 6 │ 0·509 │ 0·453 │ 0·084 7 │ 0·487 │ 0·456 │ 0·047 ─────────┴────────────┴───────────────┴────────────────────── QUALITATIVE DETECTION OF TANNINS. It is often desirable to determine from what tanning materials an extract or liquor is made, or with what a sample of leather is tanned. The following table gives reactions of the principal tanning materials, which will enable any one of them to be recognised with certainty, and in many cases will determine the constituents in a mixture of several, though this is naturally far more difficult. In such cases, colour reactions are apt to mislead, that of one tannin being modified by another, and it is safest to rely on the categorical test of precipitate or no precipitate, coloration or no coloration, without regard to the tint. The infusions must be very weak, not exceeding 1-2° Bktr., or precipitates will be formed where mere coloration or clouding is noted. In some cases only negative peculiarities can be given, and the material cannot be positively determined in mixture with materials where these peculiarities are present. Thus myrobalans could not be distinguished from divi with certainty, where any other material, such as gambier, was present, which gave a deep coloration with concentrated sulphuric acid. The writer will feel greatly obliged by the communication of more distinctive reactions. CHEMICAL ANALYSIS FOR THE TANNERY