18 DISTILLATION OF BESINOUS WOOD BY SATURATED STEAM. 

 DISCUSSION OF RESULTS. 



Table 3 gives the conditions of the distillations and the results 

 obtained. Under "Size of chip" the length parallel to the grain is 

 given first. The probable error in the determinations of yields is 

 apparently about 6 or 7 per cent and is due to difficulties in sampling, 

 in regulating evaporation during the preparation of material, and in 

 obtaining comparable end points in different distillations. An exam- 

 ple of results which must be due to such errors is seen in runs 23 and 

 24. The chips in run 24 are larger than those in run 23, and the yield 

 probably should be less, and certainly not greater, from the larger 

 chips; yet the yields obtained from run 23 are 5 per cent less than 

 those from run 24. A similar example is shown in runs 30 and 31. 

 It might be thought that some of these variations in yields were due 

 to incomplete distillation caused by the steam " channeling" through 

 the charge in such a way that it never touched part of the wood; but 

 in several runs, after all possible oil had been distilled under one set of 

 conditions, the top of the retort was removed, the charge was well 

 stirred, and the distillation continued under the same conditions as 

 before, without any indications that the stirring had discovered undis- 

 tilled material. It seems probable, therefore, that with a retort of 

 the shape and size used' the effect of incomplete distillation due to 

 incomplete contact between the steam and the chips is negligible. 



The values given under " Efficiency" are obtained by dividing the 

 yields per pound of wood by the number of liters of total distillate, 

 the efficiency factor being cubic centimeter of oil per pound of wood 



C* C* Oil 



per liter of distillate, or - ^- .. ,. , . It might be 



pounds wood X liters distillate 



thought that this " efficiency factor" would have more significance 

 if it represented only the relation between oil and total distillate; but, 

 as will be seen later, 1 this relation would be affected by the quantity 

 of wood distilled. Of course the effect may not be in exact propor- 

 tion to the quantity of wood, but it is probable that more nearly 

 comparable efficiency factors are obtained by including it. These 

 factors represent approximately the relative quantities of oil obtained 

 in the various runs per unit of steam consumed, and of course ex- 

 clude the steam which supplies the heat losses from other causes, 

 such as radiation. 



EFFECT OF SIZE OF TCHIP ON YIELD AND EFFICIENCY. 



In general, the smaller the chip the larger the yields and the higher 

 the efficiency. This is shown in Table 4, which contains selected 

 data from Table 3. Four groups of distillations are given, in each 



i The reasoning given on page 19 regarding the effect of the size of retort on efficiency applies also to the 

 effect of the amount of wood on efficiency. 



