September 12, 1902.] 



SCIENCE. 



425 



recent years. The Bavarian chemist Fuchs 

 in 1820 applied the newly discovered sili- 

 cate of soda to the fireproofing of wood and 

 employed it in the rebuilding of the Munich 

 theater for the treatment of both the wood 

 work and the hangings of the theater. Gay 

 Lussac in 1821 suggested the salts of ammo- 

 nia and borax. Tungstate of soda also 

 figured at an early day in the list of fire- 

 proofing salts as well as the salts of zinc 

 and the chlorides of the alkalies and cal- 

 cium and magnesium. Antedating all of 

 these, however, going back indeed to the 

 records of ancient Greece and Rome, was 

 alum, which has always been a favorite fire- 

 proofing material, used both alone and in 

 admixture with other compounds. 



All of these materials can under circum- 

 stances exert a notable fire-retarding effect 

 and have served as the basis of a variety of 

 patented processes for the treatment of 

 wood. 



But we must not lose sight of the fact 

 that the problem of satisfactorily impreg- 

 nating wood for fireproofing purposes is a 

 mechanical as well as chemical one and it 

 will be best to look at the mechanical side 

 of it for a few moments. The typical ap- 

 paratus until recently employed every- 

 where wherewith to saturate lumber with 

 fireproofing solutions was a large cylinder, 

 running from 60 in. diameter and 70 to 80 

 ft. long to 84 in. diameter and 105 ft. long ; 

 closed at one end, with a movable head at 

 the other, swinging horizontally or lifting 

 vertically to open or close. It was fastened 

 when closed by a complicated system of 

 radial bolts to the external end of the cyl- 

 inder. The cylinder itself, composed of 

 steel plates riveted together, was intended 

 to be filled with truck loads of lumber and 

 when the entrance door was closed and lock- 

 ed, the wood was sub.jected, after some pre- 

 liminary treatment, to hydraulic pressure 

 through the medium of the treating solu- 

 tion, which envelopes the surface of each 



piece of lumber and which the pressure was 

 intended to force into it at every point. 



With cylinders of such enormous diam- 

 eters and riveted plates, the pressure that 

 can be withstood is relatively light and as 

 a consequence the time of saturation is 

 necessarily long. 



The preliminary treatment before re- 

 ferred to is usually a steaming of the wood, 

 followed by application of a vacuum for the 

 purpose of facilitating the final step o f im- 

 pregnation. A pressure of 150 lbs. is quite 

 as much as can be maintained as an aver- 

 age in such a cylinder and to effect a com- 

 plete saturation, even with soft woods one 

 inch thick, requires in such a case from 36 

 to 40 hours. A core saturation in heavier 

 timbers such as 4 x 4 in. or 6 x 6 in. is rare- 

 ly if ever obtained even in soft woods, and 

 never in the hard woods. 



A radical improvement upon this meth- 

 od of working was effected by Mr. Jos. L. 

 Ferrell, of Philadelphia, in the invention 

 of the apparatus now in use by the U. S. 

 Fireproof Wood Co. of Philadelphia, and 

 which was described and figured in the 

 Scientific American of July 28, 1900. By 

 the replacement of the hinged gate by a 

 heavy gate, sliding between vertical guides 

 against a phosphor-bronze bearing and 

 placed in a massive gate housing near the 

 end of the cylinder, which is of heavy cast 

 tubing, he was able to use pressures rang- 

 ing from 400 to 1,500 pounds in extreme 

 cases. By the intervention of a hydraulic 

 accumulator he was able to perfectly cush- 

 ion the shock of the high-pressure pumps 

 so as to prevent all bruising of the wood 

 when under strong pressure. No prelimin- 

 ary steaming or vacuum is necessary, but 

 after the receiver is full of liquid and the 

 pressure is applied, the liquid penetrates 

 and, in what seems an incredibly short 

 space of time, has followed the medullary 

 rays from end to end of the lumber and ef- 

 fected what is bound to be a thorough core 



