THE CREOSOTE PROCESSES.
The Ruep ing and Lowry processes have for their object the wide diffusion throughout the wood of limited quantities of creosote. In both cases air-seasoned wood is preferred, although in the Mieping Process green woods can be and frequently are treated after they have been prepared by steaming and vacuum as in the Hayford Process.
Finally, the pressure is released when the air which was first introduced within the wood expands and drives out much creo sote. A vacuum which follows assists in this result. Consider able oil thus recovered is referred to as "kick-back." The pene tration obtained during the Rtieping Process may be as deep as that secured during the Bethel Process, while at the same time much less creosote is required. The Rfieping Process is used extensively in the United States and in Europe.
The Rueping Process is detailed by a railway company' located in the southeastern part of the United States, as follows : "Compressed air is pumped into the main cylinder which is filled with timber, and into the Rueping cylinder which is filled with creosote. This integral air pressure, which amounts to from twenty-five to seventy five pounds per square inch, is the means by which the final amount of oil to be retained in the wood is regulated.
"The cylinder containing the timber and the Rueping cylinder con taining the creosote being under the same pressure, the oil in the Rueping cylinder is directed into the main cylinder without decreasing the pres sure in the latter cylinder. Additional pressure, amounting to about one hundred pounds, is now applied to the contents of the main or heat ing cylinder by means of pressure pumps. If the initial pressure was sixty-five pounds, the pressure would now be about one hundred and sixty-five pounds to the square inch. The amount of the pressure and the duration of the period during which it is applied are determined by experience.
"On the completion of the pressure period a valve is opened and the pressure released. The one hundred pounds of pressure last applied is itself first released after which the initial pressure escapes. The initial pressure coming from the interior of the timber drives out the loose creo sote and leaves only the walls of the cells coated. A vacuum is drawn and the charge is released." The Lowry Process.
This process differs from that just described in that compressed air is not employed. The wood is first and the air present naturally in wood thus dried is assumed to be sufficient to drive out superfluous creosote after the antiseptic has been introduced by methods similar to those used in the Rueping Process. The Lowry Process also aims to secure a deep penetration of creosote with less oil than is required by the Bethell or Full-cell Process. The Lowry Process is extensively used throughout the United States.'