FISH ISINGLASS AND GLUE. 11 



of these cements are prepared, particularly by the addition of some 

 adhesive gum which will render the cement insoluble in water. Fol- 

 lowing is the formula for one of these : 10 grams isinglass, 5 grams 

 gum ammoniac, 5 grams mastic, 80 grams alcohol. The isinglass and 

 gums are dissolved separately in the alcohol and then heated together 

 over boiling water. The excellent properties of isinglass as a glue 

 may be illustrated by the fact that leather belts for machinery are 

 repaired by the use of this agent. (In the trade it is often called 

 Eussian fish glue.) 



Court plaster is made with isinglass as the adhesive. The pro- 

 portions used are 10 grams isinglass, 40 grams alcohol, 1 gram 

 glycerin, and water and tincture of benzoin in sufficient amount. 

 The isinglass is dissolved in enough water to make the total weigh 

 120 grams. One-half of this solution is spread in successive layers, 

 with the aid of a brush, on taffeta stretched on frames; each layer 

 is allowed to dry before the next is applied. The second half of the 

 isinglass solution is mixed with the alcohol and glycerin, and is 

 applied to the cloth in a similar manner. The reverse side of the 

 taffeta is covered with a layer of tincture of benzoin and allowed to 

 dry. The above quantities are sufficient to cover a piece of taffeta 

 38 centimeters square. 



Mixed with a gum, isinglass has been used as a size for textile 

 goods, imparting a luster and stiffness to linens and silks. Com- 

 bined with water, Spanish liquorice, and finely divided carbon, In- 

 dia ink may be made. A patent for waterproofing fabrics has been 

 obtained by Van Winkle and Todd (English patent 20G90, 1890), 

 who recommend a combination of isinglass and pyroxylin dissolved 

 in acetic acid; experience has shown that a bichromate must be 

 added to the mixture or the isinglass rendered insoluble by formalde- 

 hyde for the mixture to be successfully used. Isinglass has in past 

 years been used to adulterate milk, the addition of a small amount 

 adding considerably to the body. 



The manufacture of isinglass in this country is rather inconsider- 

 able as compared with the supply of fish sounds. According to the 

 census of 1908 ("Fisheries of the United States in 1908," p. 282), 

 the value of the annual production of isinglass in this country was 

 reported to be $150,000, all of this coming from Massachusetts. 



FISH GLUE. 



Glue is gelatin contaminated usually with various decomposition 

 products such as gelatoses, peptones, and organic acids. The purer 

 the gelatin the better glue it yields, so that a good glue should be as 

 free as possible from other proteins, from hydrolytic splitting prod- 



