L. MECHANICS AND ENGINEERING. 431 



L. MECHANICS AND ENGINEERING. 



PRESERVATION OF WOOD. 



According to Lostal, wood is rendered quite hard, and ca- 

 pable of resisting decay for a long time, by covering it in a 

 large cistern with unslaked lime, and adding water from time 

 to time until the lime is slaked, and allowing it to remain, 

 according to the size of the pieces, until it is sufficiently pen- 

 etrated by the lime-water; for that to be used in mining 

 operations a week will suffice. IS C, February 9, 1876, 95. 



CARBOLIC ACID AND THE PRESERVATION OF WOOD. 



The impression that a solution of carbolic acid has a pre- 

 servative action on wood, founded on the assumption that tar 

 preserves wood by reason of the carbolic acid and creosote 

 it contains, is asserted by M. Boucherie to be entirely er- 

 roneous. Samples of different kinds of wood impregnated 

 with one-half per cent., one per cent., and two per cent, solu- 

 tions of carbolic acid, and then buried in a soil rich in humus, 

 were found to be as completely decomposed after six years 

 as samples that had not been so treated, while others impreg- 

 nated with one and a half per cent, solution of sulphate of 

 copper were unchanged. 28 C, IV., 66. 



NEW PROCESS FOR THE PRESERVATION OF WOOD. 



A new process for preserving wood from fire and decay 

 has been invented by Messrs. Weatherby and Moore. It con- 

 sists first in kiln-drying the wood, which deprives it of all 

 moisture, and much of its volatile turpentine and other inflam- 

 mable matters. It is then put into suitable cylinders, in 

 which lime and water, with sulphurous acid gas, are forced 

 into the pores of the w^ood under considerable pressure. The 

 wood is removed, dried, and is then ready for use. The chem- 

 istry of the process consists in the formation of a soluble sul- 

 phate of lime by means of the sulphurous acid and the lime; 

 this crystallizes as a bisulphite, which oxidizes and is convert- 

 ed into the sulphate of lime or gypsum. As this is an exceed- 

 ingly insoluble salt, it is not easily removed from the pores 



