DISTILLATION OF STUMPWOOD. 23 



or air spaces, the weight decreasing as the cubical content increases. 

 An increase of about 10 per cent is said to result from reducing 

 average cordwood to the size in which the wood making up the 

 samples used in this work was piled and measured, from which 

 it would appear that the weights per cord on which the yields are 

 computed should be increased by 10 per cent. Owing, however, to 

 the irregular shape of the pieces of stump cordwood and the care 

 observed in piling the reduced wood closely, it is believed that the 

 observed weights are not essentially lower than the average weight 

 of a commercial cord of western yellow-pine stumpwood of corre- 

 sponding quality. In support of this it was found that of the 3 

 cords of stumpwood from near Deary, Idaho, piled and measured 

 in the field, when corded again after having been reduced to the 

 size in which they were used in the retort, one measured an even 

 cord, one 19 per cent less than a cord, and the third 10 per cent 

 more than a cord. It seems unnecessary, therefore, to use other 

 than the observed weights in calculating results. 



The retort distillations were made on charges of known weights, 

 varying from 150 to 200 pounds, depending on the nature of the 

 wood. The distillation products were measured in liters per charge 

 and the yields reported in gallons per cord. This basis of state- 

 ment was selected in preference to the more exact unit-of-weight 

 basis, the ton, for example, because of the difficulty of estimating 

 the quantity of the several classes of wood on a given acre and 

 applying the results to the problems in hand on other than the 

 cord basis. The yields can be quickly figured to the ton basis from 

 the data given in Table 14. 



APPARATUS. 



In principle, the apparatus (figs. 3 and 4) is essentially an oil- 

 jacketed retort (a) in which high-flash cylinder oil, heated to the 

 desired temperature, is circulated through closely spaced heating 

 coils (&, <?, and d) within the retort. The coil system of jacketing 

 is preferable to a double shell in that it insures a positive flow of 

 the heated oil, and, by dividing the coils into sections, prevents an 

 excessive drop in temperature between the incoming and outgoing 

 oil. A 3-inch layer of asbestos lagging and pipe covering of the 

 same material protects the retort and exterior piping against ex- 

 cessive radiation. A coarse wire-gauze screen placed on the jacket 

 coils facilitates removal of the charcoal. 



The motor-driven oil pump (/) takes oil from the overflow tank 

 (g) and discharges it through the gas-fired oil heater (e) into the 

 jacket coils (b and c), from the other end of which it flows back 

 into the tank (g). This circulation is maintained with the jacket oil 

 as it comes from the heater and is held at 260 C. as registered on 



