Green: Iodine green.
Violet: Methyl violet.
Gelatine for Fining Purposes.
For fining beer, wine, etc., gelatine in leaves or in powder is brought into commerce. For the preparation of leaves, gelatine particularly well dried is carefully melted over a water-bath and then ladled into sheet-metal moulds, and allowed slowly to solidify.
The product brought into commerce under the name of Gelatine Lainée which commands a high price is in many cases nothing but thoroughly purified bone-glue of a dark honey-yellow to brown color.
Fining powder for wine and beer is made by grinding off-color gelatine cakes and freeing the resulting powder from coarser pieces by sifting. The powder is white.
Liquid fining gelatine. This preparation consists of gelatine-solution suitably prepared, and represents a colorless, or at the utmost slightly opalescent, product just sufficiently concentrated to remain liquid.
Skin-liquors can only be used for the preparation of liquid gelatine, as bone-liquors already gelatinize when they contain scarcely more than 1 per cent. of glue. The skin liquors are concentrated so far as to remain liquid at a temperature of from 60° to 68° F.
A product answering all demands is obtained as follows: A good quality of gelatine of a pale color is dissolved in a sufficient quantity of water, the solution, in case it shows a slight odor, filtered through animal charcoal, and then brought into bottles. To prevent putrefaction the liquid gelatine is sterilized as follows:
The filled bottles being placed in a boiler filled to a proper depth with water, the latter is slowly brought to boiling which is kept up for 15 to 20 minutes. The bottles are then closed with corks previously boiled in the water.