With superheated steam a vertical retort is used, and the steam, 

 before entering the retort, passes through a superheater, which raises 

 its temperature high enough to readily volatilize the turpentine. 

 From the condensers the distillates run into a separator. 



For saturated steam several sorts of retorts are used, and the 

 steam enters them directly from the boiler. There are a number of 

 patented devices, the most important differences in which have to 

 do with methods of charging and discharging. The fundamental 

 idea, however, is to maintain a sufficient pressure of steam, through- 

 out the run, to facilitate rapid extractions. A separator is used, 

 as with superheated steam. 



PRODUCTS. 



The products of both processes are crude turpentine and water, 

 in a separator tank, and chips left in the retort. The turpentine, 

 which is lighter than water, floats on the surface and is easily drawn 

 off, ready for refining. The chips, after drying a short time in the 

 air, are suitable for fuel. 



In order to obtain a market grade of turpentine, the crude product 

 should be refined by distillation with steam in a copper still. As it 

 comes from the retort its color is slightly yellow. 



There is the same variety in methods used as in other kinds of 

 wood distillation, and consequently the same lack of uniformity in 

 the products. Much remains to be learned as to the best method 

 of refining turpentine so as regularly to secure the best grades. 



The amount of turpentine obtained from steam distillation varies 

 widely. The wood itself varies greatly in richness. A conservative 

 average per cord is given in the following table (the difference between 

 stumps and "lightwood" is slight enough to be disregarded): 



Lightwood : 



Refined turpentine 10 to 15 gallons. 



Heavy oils 1 to 3 gallons. 



Sawdust: 



Refined turpentine 2 to 4 gallons. 



Heavy oils J gallon. 



The refined turpentine is of reasonably uniform quality, is nearly 

 colorless, has an agreeable odor, and has a fair market at a price some- 

 what below the market price for gum spirits of turpentine. 



COMPARISON OF METHODS. 



Comparing the steam methods with the destructive methods, 

 although there is room for difference of opinion, it would seem that 

 the steam distillation is open to the wider development. The suc- 

 cessful destructive distillation plants are those which are run by 

 men who have remained in the business long enough to establish 

 their processes and methods and the markets for their products. 

 Turpentine, the leading product, is probably produced less expen- 

 sively by the steam method, and the steam apparatus necessary to 

 handle a given quantity of wood per day, say 50 cords, is easier to 

 ^0 per ate. 



There have been fewer failures in steam distillation than in destruc- 

 tive distillation, perhaps because it is of more recent development, and 



[Cir. 114J 



