ISINGLASS 1035 



form. In external characters it agrees with Diadochite, which is Fe 2 8 ,2P0 5 + 

 4Fe 2 8 ,S0 3 + 32HO, according to Gmelin from Plattner's analysis, viz. peroxide of 

 iron, 36-69; phosphoric acid, 14*81 ; sulphuric acid, 15-15; water, 30*35. 



11. Iron, Sulphate of; Native Green Vitriol. This is formed by the oxidation of 

 sulphide of iron. 



12. Iron, Tungstate of; Wolfram, occurs, with tin ore, forming fine crystals, at 

 Altenberg in Saxony ; at Schlackenwald in Bohemia ; and in France, in quartz veins. 

 In Cornwall, especially near Kedruth, it renders the tin ore valueless until it is 

 removed. An analysis of a specimen from Cumberland gave Berzelius, tungstic 

 acid, 78'77; protoxide of iron, 18'32; protoxide of manganese, 6*22; and silica, 1*25. 

 See WOLFBAM. 



13. Y&iite or Lievrite ; Hisingerite or Thraulite ; Nontronite ; Pinguite; and 

 Chloropal, are rather rare minerals, composed of peroxide of iron and silica. The first 

 may contain about 12 per cent of lime ; the others are destitute of this earth, but con- 

 tain from 10 to 20 per cent, of water: the amount of silica in these minerals ranges 

 between 30 and 40 per cent. 



14. Iserite. A variety of titaniferous iron-ore. 



IRON PYRITES. Native bisulphide of iron. See PYEITES. 



IRON, TELLURIC. A name given to native iron, of which there is no proof 

 of meteoric origin. See IEON. 



IRON WOOD. A name given to several of the hard, heavy, and close-grained 

 woods. The Metrosideros vera, or true iron-wood, is a native of Java and Amboyna. 

 The Chinese use it for making anchors. The Metrosideros polymorpha is the wood 

 of which the Sandwich Islanders make their clubs. Metrosideros buxifolia is a Now 

 Zealand shrub, the wood of which is called in the country AJci or Lignum vitce. Other 

 varieties of these woods are produced by the Sideroxylon, found in many tropical 

 countries. In North America the timber of the Ostrya virginica is known as iron- 

 wood. 



ISINGLASS (Colle de Poisson, Fr.; HausenUase, Ger.) IchthyocoUa, ix6v6Ko\\a, 

 from Ix6bs, a fish, and K^AAa, glue, or Fish-glue, is a whitish, dry, tough, semi-trans- 

 parent substance, twisted into different shapes, often in the form of a lyre, and 

 consisting of membranes rolled together. Good isinglass is unchangeable in the air, 

 has a leathery aspect, and a mawkish taste, nearly insipid ; when steeped in cold water 

 it swells, softens, and separates in membranous laminae. At^the boiling heat it 

 dissolves in water, and the solution, on cooling, forms a white jelly, which is semi- 

 transparent, soluble in weak acids, but is precipitated from them by alkalis. It is 

 gelatine, nearly pure ; and if not brittle, like other glue, this depends on its fibrous 

 and elastic texture. The whitest and finest is preferred in commerce. Isinglass is 

 prepared from the air-bladders of sturgeons, and especially the great sturgeon, the 

 Accipenser huso, which is fished on the shores of the Caspian Sea, and in the rivers 

 flowing into it, for the sake chiefly of its swimming-bladder. It is also obtained from 

 the A. stellatus and the A. Guldenstadtii. At Hamburg, German isinglass is made 

 from the swimming-bladder of the common sturgeon (A. sturio). We are informed 

 that in Russia the Siluris glanis is also caught for the purpose of obtaining isin- 

 glass. 



The preparations of isinglass in Russia, and particularly at Astracan, consists in 

 steeping the swimming-bladders in water, removing carefully their external coat, and 

 the blood which often covers them, putting them into a hempen bag, squeezing them, 

 softening them between the hands, and twisting them into small cylinders. They are 

 ready for the 'market immediately after being dried in the sun, and whitened with the 

 fumes of burning sulphur. 



In some districts of Moldavia another process is followed. The skin, the stomach, 

 the intestines, and the swimming-bladder of the sturgeon are cut in small pieces, 

 steeped in cold water, and then gently boiled. The jelly thus obtained is spread in 

 thin layers to dry, when it assumes the appearance of parchment. This being softened 

 in a little water, then rolled into cylinders, or extended into plates, constitutes an 

 inferior article. 



The swimming-bladder of the cod, and many other fishes, also furnishes a species 

 of isinglass, but it is much more membranous, and less soluble than that of the 

 sturgeon. 



The properties of isinglass are the same as those of gelatine or pure glue ; and its 

 uses are very numerous. It is employed in considerable quantities to clarify ale, 

 wine, liqueurs, and coffee. As an article of food to the luxurious in the preparation of 

 creams and jellies, it is in great request. Four parts of it convert 100 of water into 

 a tremulous jelly, which is employed to enrich many soups and sauces. It is used 

 along with gum as a dressing to give lustre to ribbons and other silk articles. 



It is by covering thin silk with a coat of isinglass that court-plaster is made* A 



