Page:A Practical Treatise on Brewing (4th ed.).djvu/169

Rh form of a thick jelly. The other samples which afforded a less solid jelly will give, with tincture of galls when stirred through it, a smaller quantity of gelatine in the form of thick jelly.

“From the strength of the jelly given by any sample of isinglass steeped in the above proportion of sour beer (such as brewers use in making clearings), and submitted to a temperature not exceeding 75° F., may be ascertained the relative value of that sample, as upon the strength of the jelly, and, consequently, the quantity of gelatine contained in any isinglass, depends its value in clearing malt-liquor. The best short-staple isinglass is always soluble in boiling water to about $1/50$ residue.”

From the following quotations, however, it will appear that there are objections to the use of isinglass in fining beer, except for immediate use. Berzelius, who had discovered a small quantity of lactic acid in all animal fluids, and in muscular fibre, gave it as his opinion, in 1834, that lactic acid is produced in all fermentable matter. This suggestion has been confirmed by Vanden Ghyen of Ghent, who has extracted it from the beer of Diest: De Koninch has obtained the same acid from the brown beer of Malines. One litre of the beer of Diest afforded 2.20 grams of syrupy lactic acid. (L’Institut, 284.) “M. Fremy says that the internal membrane of the stomach of the calf is capable of transforming any aqueous solution of sugar into lactic acid.” (L’Institut, 286.)