Hermann Kratzer, of Leipsic, communicates the following practical information on the clarification and purification of vinegar to the Neueste Erfindungen und Erfahrungen:
If vinegar has an unpleasant odor, which is rarer now that the vinegar manufacture has reached such a state of perfection, it may be removed as follows: Well burned and finely pulverized wood charcoal is put into the bottles containing the vinegar, the proportions being 8 grammes of charcoal to a liter of vinegar, or one ounce to the gallon. It is shaken several times very thoroughly, then left standing three or four days, and the vinegar filtered through a linen cloth. Vinegar treated in this manner will be found to have completely lost its unpleasant odor.
I have found that when I used blood charcoal or bone coal in place of wood coal it was still more efficient; but it must be mentioned that when they are used they must be purified as follows before using: Charcoal from blood contains potash and hence it is necessary to wash it with distilled water and dry it before using it. Bone coal (also called bone black, animal charcoal, etc.) contains on an average 10 per cent. of nitrogenous and hydrogenated carbon, 8 per cent. of carbonate of lime, 78 per cent. of phosphate of lime, besides phosphate of magnesia, sulphate of lime, soluble salts, etc. Before using, it should be treated with dilute hydrochloric acid until it does not effervesce any more. The bone coal is then left to stand for 24 or 30 hours and at the end of this time is washed with distilled water until the wash water no longer reddens a blue piece of litmus paper, i.e., until every trace of hydrochloric acid has been removed from the bone coal. Wood charcoal may be treated in like manner.
When this coal is perfectly dry it is employed in the same proportions as the other, 8 to 1,000, the operation being exactly the same.
He turns next to the clarification of the vinegar.
It happens everywhere that vinegar instead of being clear is sometimes turbid. This is due to particles of yeast dissolved in the vinegar that have not yet settled. To remove this kind of turbidity it is customary to use oak or beech shavings that have been washed in hot water and then dried. These shavings, which must be very long and extremely thin, are put in a barrel with a second and perforated bottom, to a depth of 12 to 34 inches. The vinegar that runs through them deposits its slimy constituents on the shavings and becomes perfectly clear, and presents to the eye a pleasing appearance.
To this generally known method I would add a few more:
1. I take a ½ kilo of well pulverized animal charcoal (black burned bones) to 7/8 of a hectoliter of vinegar (1 lb. to 20 gallons), and stir it well with a wooden rod; or, if the vinegar is in bottles, I shake it a long time after putting the animal charcoal in the bottle, and repeat it several times. After three or four days I finally filter the vinegar through linen, when the filtrate will exhibit the desired clearness.
2. The best way to clarify vinegar is with isinglass. It is first broken up, then swelled for a day in vinegar (17 or 18 grammes to the liter), then 2 liters of vinegar are added and the mass boiled until the isinglass is completely dissolved. Such a solution as this (½ ounce to 3 quarts) is mixed with 10¼ hectoliters (250 gallons) of turbid vinegar and well stirred through it. After the expiration of five or six weeks vinegar treated in this way has a beautifully clear appearance.
3. Albumen can likewise be used to clarify it. The vinegar is boiled with the albumen until the latter is completely coagulated, and then the vinegar is filtered.
4. And finally milk may be employed. For this purpose the milk is skimmed, and 1 quart of milk added for every 68 quarts of vinegar, the mixture well stirred and shaken. After the caseous portion has coagulated (curdled) it is filtered as before, and in this case, too, the product is a fine, clear vinegar.
We believe that these few experiments, so easily performed, and at so small an expense, will prove useful to our readers in enabling them to put their product in the market in an excellent condition and nicely clarified.