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Isinglass

fish, sounds, roll, staple, called, sorts and former

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ISINGLASS, used in medicine and do mestic economy, is a preparationformerly made only from a fish named huso, a spe cies of the Accipenser genus. We have, in the sixty-third volume of the transactions of the Royal Society, a full account of the mode of preparing this substance, of which we shall give an extract.

The sounds, or air-bladders, of fresh water fish in general, are preferred for this purpose, as being the most transpa rent, flexible, delicate substances. These constitute the finest sorts of isinglass; those called book and ordinary staple are made of the intestines, and probably of the peritonxum of the fish. The belluga yields the greatest quantity, as being the largest and most plentiful fish in the Mus covy rivers ; hut the sounds of all fresh water fish yield, more or less, fine isin glass, particularly the smaller sorts, found in prodigious quantities in the Caspian sea, and several hundred miles beyond Astracan, in the Wolga, Valk, Don, and even ar far as Siberia, where it is called kle or kla by the natives, which implies a glutinous matter; it is the basis of the Russian glue, which is preferred to all other kinds for its strength. The sounds, which yield the finer isinglass, consist of parallel fibres, and are easily rent longitu dinally; but the ordinary sorts are found composed of double membranes, whose fibres cross each other obliquely, resem bling the coats of a bladder ; hence the former are more readily pervaded and divided with subacid liquors ; hut the latter, through a peculiar kind of inter woven texture, are with great difficulty torn asunder, and long resist the power of the same menstruum ; yet, when duly resolved, are found to act with equal energy in clarifying liquors.

Isinglass receives its difFerentIshapes in the following manner. The parts of which it is composed, particularly the sounds, are taken from the fish while sweet and fresh, slit open, washed from their slimy sordes, divested of every thin membrane which envelops the sound, and then ex posed to stiffen a little in the air. In this state, they are formed into rolls about the thickness of a finger, and in length according to the intended size of the staple : a thin membrane is generally se lected for the centre of the roll, round which the rest are folded alternately, and about half an inch of each extremity of the roll is turned inwards. The due di.

mensions being thus obtained, the two ends of what is called short staple are pinned together with a small wooden peg ; the middle of the roll is then press ed a little downwards, which gives it the resemblance of a heart-shape, and thus it is laid on boards, or hung up in the air to dry.

The sounds, which compose the long staple, are longer than the former ; but the operator lengthens this sort at plea. sure, by interfolding the ends of one or more pieces of the sound with each other. The extremities are fastened with a peg, like the former ; but the middle part of the roll is bent more considerably down wards, and, in order to preserve the shape of the three obtuse angles thus formed, a piece of round stick, about a quarter of an inch diameter, is fastened in each an gle with small wooden pegs, in the same manner as the ends. In this state, it is permitted to dry long enough to retain its form, when the pegs and sticks are taken out, and the drying completed ; lastly, the pieces of isinglass are colligated in rows, by running pack-thread through the peg holes, for convenience of package and exportation. That called cake-isinglass, is formed of the bits and fragment s of the staple-sorts, put into a flat metalline pan, with a very little water, and heated just enough to make the parts cohere like a pancake when it is dried ; but frequently it is overheated, and such pieces, as be fore observed, are useless in the business of fining. Experience has taught the con sumers to reject them.

Isinglass is beat made in the summer, as frost gives it a disagreeable colour, de prives it of weight, and impairs its gela tinous principles; its fashionable forms are unnecessary, and frequently injurious to its native qualities. It is common to find oily putrid matter, and exuvix of in sects, between the implicated membranes, which, through the inattention of the eel larman, often contaminate wines and malt liquors in the act of clarification.

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