The Isinglass of Commerce. 241 



provided it contains as much as one-hundredth of its 

 weight of gelatine, has the property of gelatinizing or 

 assuming the form of a soft, tremulous solid as it cools. 

 The inferior sorts are thick, opaque, white, or yellow, 

 having a fishy taste and smell, and only partially dissolve. 

 The commonest kind, termed cake isinglass, is of a brownish 

 colour, having an unpleasant smell, and is only used in the 

 arts, and for the preparation of glue. The Brazilian isin- 

 glass is very inferior to the Russian, and is in the form 

 of pipe, block, honeycomb, cake, and tongue isinglass. 

 The North American is like long ribbons, produced from 

 the air-vessels of the Otolithus regalis, Bl. Schn. 



Russian Isinglass. Isinglass is obtained in Russia from 

 .the interior lining of the swimming-bladder of the sturgeon 

 (Accipenser), the Silurus glanis, the Lucioperca Wolgensis, 

 Pall., and the large carps. The Coregonus leucichtys also 

 furnishes a little. 



The air-bladders are left for some days in water, which is 

 frequently changed, in order to remove the fatty and bloody 

 particles ; they are then withdrawn and cut lengthwise into 

 sheets, which are exposed to the sun and air, the outer part 

 being attached to boards. The inside, which is formed of 

 layers of pure isinglass, is carefully detached from the ex- 

 terior layers, wrapped in linen, and pressed, in order to 

 keep it from contracting ; it is then made up into parcels 

 according to size. The parcels of isinglass of the large 

 sturgeon are composed of from 10 to 15 sheets, and weigh 

 about a pound and a quarter ; those of the ordinary 

 sturgeon contain 25 sheets, and weigh one pound. These 

 parcels, to the number of 80, are packed in a linen bag, 

 covered with rush matting, and sent away sealed with lead ; 

 38 Ibs. are worth, at Astrakhan, from 19 4*. to 28 16^., 

 according to quality. The air-bladder, although deprived 



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