Page:A Practical Treatise on Brewing (4th ed.).djvu/170

154 “M. Gay Lussac cautions, however, against the conclusion, that this change is an organic one, since it is possible that the transformation may be due to an action purely chemical between the saccharine and organic" matter. Indeed, we know that lactic acid is in many cases produced by the contact of animal with vegetable substances.” (L’Institut, 288.)

Having thus stated objections which may be raised as to using isinglass for fining beer, we shall give the mode of preparing it for use. Chemists state that gelatine is dissolved in liquid alkalis. The common mode, however, of converting isinglass into finings for beer, is by dissolving it in the first place by acids. Let any quantity be taken which may be thought necessary according to the magnitude of the brewery, and placed in an open-headed cask: if cut into shreds it will dissolve the more quickly. Let it then be covered to the depth of five or six inches with vinegar, which is the best solvent, or with very acid old beer. When the isinglass has swelled up so as to have absorbed all the vinegar or old beer on the top, more vinegar or old beer must be added, again covering the mass to the depth of five or six inches: the mixture should then be vigorously stirred with a hard broom, and the same process repeated as the isinglass goes