(jct. — dec. 1857.] Mode of protecting Timber from Fire, 123 



3rd. That prepared surfaces of wood, when in actual contact 

 with burning unprepared wood, shall have little tendency to ignite, 

 and thereby cause the fire to spread. 



In addition to such processes as those above referred to, in 

 which the protecting material is forced into the wood by the ap- 

 plication of considerable pressure, trials have been made with 

 agents of different kinds, in solutions or baths, in which the wood 

 was steeped, or allowed to soak, for some hours, so that it might 

 be in a slight degree impregnated with the material, or that a 

 superficial coating of the protective might, at least, be formed. 



Some of these methods have been made the subject of experi- 

 ments by order of Lord Panmure, with a view to test their merits. 



One, proposed by W. C. Salomons, of Paris, consisted in immer- 

 sing the dried wood alternately, in two baths ; the one containing 

 three parts of acid sulphate of alumina, and one part of glue, 

 dissolved in six parts of water ; the other consisting of two parts of 

 dry chloride of calcium, one part of glue, and seven parts of water. 



The objects Which the inventor wishes to attain, by the use of 

 these solutions, are, firstly, to impregnate the wood slightly with 

 one of the salts (the chloride of calcium, for example), and then, 

 by immersion of the wood in the second bath, to effect the decom- 

 position of the first salt by the second, in the pores of the wood. 



Thus the chloride of calcium and sulphate of alumina should 

 become converted into sulphate of lime, and chloride of aluminum ; 

 the former an almost insoluble substance, the latter a soluble 

 deliquescent body, possessing the property of converting the glue., 

 employed, together with the salts, into an insoluble body — a species 

 of leather. 



The pores of the wooden surfaces are therefore, by the treatment 

 in question, to be filled up by particles of a substance nearly inso- 

 luble, and unalterable by heat, which, together with the soluble 

 salt, also present, are to be protected and united by means of the 

 precipitated glue, which dries up to a hard, horny substance. 



The experiments made with this process showed that the glue 

 employed in the solutions greatly impeded the penetration of the 

 wood by the saline matter, and also caused the decomposition of 

 the salts to be very partial. 



