M. TECHNOLOGY. 519 



every pore. A pressure of about fifty pounds to the square 

 inch, for half an hour, is sufficient for this part of the process. 

 After the wood has become completely saturated with the 

 caustic, the excess of the latter is pumped away, to be used 

 over again. The vessel in which this operation has been 

 carried on is provided with a double envelope, so that be- 

 tween its walls steam can be introduced. The wood is thus 

 heated up to nearly 300 Fahr. for two hours, at the end of 

 which time its fibres can be easily separated by washing. 

 This washing is continued until the escaping wash-water is 

 perfectly limpid. A semi-pulp is the result of this process, 

 which can be easily converted by ordinary means into a pulp 

 suitable for the manufacture of paper. Bleaching may be 

 performed either before or after this conversion, according to 

 the color or quality of paper to be produced. In the entire 

 process but little soda is realty consumed, little time is wast- 

 ed, and the woody fibres are completely freed from all resin- 

 ous substances. 9 J3, February 26, 1874, 97. 



PURE COLLODION FROM CELLOIDINE. 



A manufacturer in Berlin has succeeded in purifying gun- 

 cotton in a cheap way, and in furnishing celloidine cotton or 

 paper, as it is called, which affords a perfectly clear solution 

 with ether and alcohol mixture. Furthermore, this does not 

 cause separation of iodine from iodides not already decom- 

 posed by action of the air (as does iodide of ammonium), 

 even after a long time ; and the iodized collodion of this proc- 

 ess which may be kept on hand is said to possess all other 

 desirable properties. 13 C, July 1, 1873, 802. 



PREPARATION OF RUSSIAN ISINGLASS. 



The Russian isinglass, as it appears in commerce, is made 

 from the swimming-bladder of the sturgeon, especially of the 

 variety known as the Belouga (Acipenser huso). When of 

 good quality, it should be pure white, brilliant, semi-trans- 

 parent, dry, and horny in texture, and free from smell. It 

 should dissolve in water heated to 90-120 Fahr., without 

 any residue, and in cooling should produce an almost color- 

 less jelly. This isinglass is generally prepared by boys, un- 

 der the supervision of older experts. The swimming-bladder 

 is first placed in the water and left there for some days, with 



