12 WOOD TURPENTINE. 



This method has been studied by this bureau and by other investi- 

 gators, and is perfectly simple and feasible, but for the reasons men- 

 tioned it remained undeveloped until very recently. It is now being 

 placed on a commercial basis. 



The following diagram shows the products obtained from resinous 

 wood by extracting with volatile solvents and the utilization of the 

 extracted chips: 



[Extract 



Resinous wood... J (distilled) 



(hogged and extracted with volatile solvent) 



Chips. 



Distillate /Solvent. 



(fractionated) \Wood turpentine. 

 Residue (strained) =rosin. 

 Destructively distilled (see p. 10.) 

 Wasted or burned. 



Digested with caustic soda= paper pulp. 



Several processes have been developed which make use of a liquid 

 having a higher boiling point than turpentine. Melted rosin, pitch, 

 tar, pine oils, or crude gum turpentine are suitable in starting the 

 plant, but as a matter of fact the bath finally consists of rosin, because 

 of the fact that the volume is constantly increased by rosin removed 

 from the wood. In such processes the liquid passes through a super- 

 heater, where its temperature is raised to about 200 C., and thence 

 to a closed retort containing the wood so prepared as to insure rapid 

 penetration by the liquid. In returning to the superheater the hot 

 rosin passes through a still and the turpentine is distilled from it. 

 The liquid is finally drained from the exhausted wood and used on 

 subsequent charges. The advantages of this process over simple 

 distillation with steam are that the treated wood is left in such 

 condition that it may be sold for fuel, used as paving blocks, or 

 subsequently destructively distilled without contaminating the 

 wood turpentine with rosin spirits or other products of destructive 

 distillation. 



The recovery of turpentine and rosin by extraction with alkalis 

 and the use of the extracted wood for making paper is a process which 

 has been experimented with, and one mill is operating on mill waste, 

 making turpentine and wrapping paper. In this process also the wood 

 is cut up in the same way as for making paper pulp and treated with 

 an excess of soda in solution. The turpentine may be removed 

 by simple steaming previous to adding the soda solution, or it may 

 be steamed off during the cooking with soda. The latter procedure 

 has the advantage of requiring less time to complete the treatment 

 of the wood. The cooking with soda may be conducted in several 

 ways. The contents of the retort may be heated only sufficiently to 

 dissolve the rosin without attacking the wood, after which the solu- 

 tion may be drawn off nearly free from ligneous materials, and the rosin 

 or rosin oils recovered from it, or the wood may be cooked with the 

 soda solution at 'a high temperature. 



After the completion of the treatment the soap solution of soda 

 and rosin, containing also the dissolved ligneous material, is drained 



