198 Processes for Wood-preservation. 



784 The Payne Process, patented in England in 1841. This con- 

 sists in' using two solutions, one after the other, and both soluble, 

 but forming an insoluble substance within the wood. The earthy or 

 metallic solution is first introduced under pressure ; after which the 

 decomposing fluid is forced in. The sulphate of iron and carbonate 

 of soda are said to form the insoluble compound in the pores of the 

 wood. He tried a mixture of the sulphate of barium or of calcium 

 with the sulphate of iron, and various other compounds. The pro- 

 cess was costly and imperfect, and is now abandoned.' 



785. By Prechtl's Process ( 1822) the wood is first exposed to the 

 vapor of water alone, and then to that of a mixture of tar and 

 water. 



786. The BobbMs Process ' consists in first removing the surface 

 moisture of the wood by heat, and then thoroughly impregnating 

 and saturating the pores and fibers by oleaginous vapors, as of coal- 

 tar, resin, or other substances, the temperature being from 212° to 

 250° (F.) for the former, and about 300° or more for the latter part 

 of the process. 



787. The Tait Process consists in saturating the pores of the wood 

 with a concentrated solution of bi-sulphate of lime or baryta, the 

 same being rendered soluble by an excess of sulphuric acid gas under 

 pressure, or by refrigeration, and being made insoluble as a neutral 

 sulphate, when the pressure or excess of gas is removed. 



788. Tlte Thilmany Process ' consists in saturating the wood first 

 with a solution of the sulphate of copper, followed by one of the 

 muriate of barytes, the intention being to form an insoluble sulphate 

 of barytes within the wood. 



789. The following application has been recommended as valuable 

 in a German journal : " Melt 12 pounds of resin, and add 12 pints 

 of whale oil and 3 pounds of sulphur ; mix an ochre of the color 

 desired, mix very thoroughly in oil, and add. Apply at first a 

 light coat white hot, and in two or three days, when well dried, a 

 second and a third one." This is intended for fences and other 

 wood-work much exposed. 



* Boston City Docs. No. 100, 1873 ; in a Prize Essay by Prof. F. W. Clarke, 

 p. 15. 



* Patents were taken out by Louis S. Bobbins, April 4, 18C5 ; April 27, 

 1869 ; July 20, 1875, and Dec. 21, 1880. 



'Patented by W. Thilmaiij', May 2A, 1876. 



