M. TECHNOLOGY. 543 



a fire beneath it to such a degree that the hydrochloric acid 

 is vaporized rapidly, while the draft of the lire circulates 

 around it so that it is warmed on all sides. After half an 

 hour the carriage is run out, the rags are turned about, and 

 it is run in again ; the operation being repeated until, upon 

 testing the rases with the fino-ers, it is evident that the cotton 

 is entirely disintegrated. The rags are then neutralized in 

 water containing whiting, and afterward dried. With woven 

 material it is better to carbonize it by working it half an hour 

 in sulphuric acid of 12 Baume, containing two pounds of 

 oxalic acid and two pounds of common salt, well stirred to- 

 gether and warmed, and then allowing it to remain in the 

 bath without working for 1^ hours, and after letting it drain, 

 on removal from this bath, drying it at 113 to 122, and im- 

 mersing it in a weak solution of soda to neutralize the acid, 

 and finally washing it in pure water and drying. 24 C, 

 171. 



PHOTOGRAPHIC IRRADIATION. 



In order to prevent the irradiation attending the photo- 

 graphing of the sun, or other bright object, Mr. Stillman 

 states that the most effectual means, where the dry process 

 is available, is to allow the collodion to be acted upon by a 

 laro-e excess of nitrite of silver for a considerable time, and 

 then to convert this into bromide of silver by the addition 

 of ammonium bromide. The result is that the film has a 

 dull, opaque character, like unglazed porcelain, and not only 

 stops the light more completely than an ordinary collo- 

 dion film, but reduces another cause of irradiation, namely, 

 the molecular reflection of the film itself. 12 A 9 X., 1874, 

 63. 



A SUBSTITUTE FOR IVORY. 



A substance under the name of celluloid, the invention of 

 Mr. Hyatt, of Albany, originally intended as a substitute for 

 ivory in the manufacture of billiard-balls, possesses qualities 

 which render it applicable to a great variety of manufactures. 

 As originally prepared, it consisted of a combination of solu- 

 ble cotton and ether or alcohol, but it was subsequently as- 

 certained that a still more satisfactory result could be obtain- 

 ed by the addition of camphor to the alcohol; and, finally, 



