Oct. 1, 1864.] THE TECHNOLOGIST. 



ON CHEMISTRY APPLIED TO THE ARTS. 99 



run into another pan, where it is concentrated to the necessary consist- 

 ency, so as to become solid, when it is run into wooden moulds. Eighteen 

 hours afterwards the gelatine in turned out of these moulds on to a wet 

 slab, where it is cut into slices by means of a copper wire ; these slices 

 are placed on wire gauze frames, and left in a drying shed until they are 

 perfectly dry and ready for the requirements of trade. The second 

 quality of gelatine is prepared by placing bones in large cylinders, and 

 allowing high-pressure steam to arrive at the bottom of the cylinder, 

 which rapidly converts the osseine of the bones into gelatine, and the 

 removal of this is facilitated by allowing a stream of hot water to enter 

 the upper part of the cylinder. The solution of gelatine thus obtained 

 is evaporated, and is usually employed for the preparation of glue. A 

 third quality is prepared by treating bones with hydrochloric acid (as 

 referred to in my first lecture), and submitting the osseine thus obtained 

 to the action of steam. Lastly, a fourth quality of gelatine, called 

 bone-size, is manufactured by boiling more or less decayed bones as im- 

 ported from South America and elsewhere, the flesh of dead animals, 

 &c, and concentrating the solution to the consistency required for the 

 various applications it receives in commerce. [The lecturer then 

 described the mode of obtaining the beautiful thin coloured sheets of 

 gelatine used in photography and other fancy purposes, and also the 

 characteristics which distinguished good from bad glues.] 



Chondrine, or cartilage gelatine, first noticed by Messsrs. Miiller and 

 Vogel, j un., is interesting as possessing qualities not only different from 

 those of gelatine, but such as injure the quality of the latter when mixed 

 with it. In fact, it gives precipitates with acetic acid, alum, persulphate 

 of iron, and other salts ; and as gelatine is often used in connection with 

 these substances, it is easy to foresee how these precipitates may inter- 

 fere with its application. On the other hand, the quality possessed by 

 this peculiar gelatine may, 1 think, render it serviceable in the art of 

 calico printing, for fixing colours, or as a substitute for albumen or 

 lactarine. Thus, the solution of chondrine and acetic acid may be 

 mixed with any of the new tar colours, and the whole printed, allowed 

 to dry, and steamed ; the acetic acid will be driven off, leaving the 

 colour fixed by the chondrine on the fabric. Chondrine is prepared by 

 submitting to the action of heat and water the cartilaginous tissue of 

 animals or the bones of young animals. 



Isinglass is obtained from the air-bag, or swimming-bladder, of several 

 kinds of fish, especially those of the Sturgeon tribe ; and although im- 

 ported from various parts of the world, the principal supplies are from 

 Eussia, from whence the best qualities come, which bear the names of 

 Beluga, Volga, or Caspian Sea leaf. Brazil, New York, the East Indies, 

 and Hudson's Bay, also supply various qualities of this valuable sub- 

 stance. It also reaches this country in different states, viz., in leaf and 

 in honeycomb, that is, the bag is cut open, cleaned, and dried ; and the 

 quality called snow-bleached is enhanced in value by having been 



