158 PROCEEDINGS OF THE AMERICAN ACADEMY 



very small to have escaped notice so generally. The wood, chiefly 

 oak, is cut into small pieces and filled into rectangular retorts of boiler 

 iron, each one capable of holding a charge of from five to six thou- 

 sand kilogrammes. The retorts when charged are placed in separate 

 cells of an oven heated by hot-air flues. The temperature of this 

 oven is carefully regulated by means of long mercurial thermometers 

 built into each cell, and the thermometer readings vary from 150° at 

 the beginning of a distillation to 200° at the end. The average time 

 required is six days, and during this time the wood loses about thirty- 

 two per cent of its weight. The volatile products pass through an 

 outlet pipe at the top of each retort, and are condensed in a set of 

 ordinary coolers. 



The wood left in the retorts after distillation is darker in color and 

 somewhat more brittle than the fresh wood : its composition agrees 

 essentially with that given by Payen * for dried oak wood. The 

 specimens of wood for analysis were taken while still warm from 

 the I'etorts, and kept hermetically sealed until analyzed. 



I. 0.4480 grm. substance gave 0.8950 grm. CO,, 0.2545 grm. B^O 

 and 0.0040 grm. ash. 

 II. 0.3880 grm. substance gave 0.7810 grm. COj and 0.2220 grm. 

 II2O. 1.2725 grm. of the same wood gave 0.0070 grm. ash. 

 III. 0.3270 grm. substance gave 0.6390 grm. CO2, 0.1740 grm. HjO 

 and 0.0015 grm. ash. 



The volatile products of the distillation are subjected to the ordinary 

 processes of rectification. In fractioning the wood spirit, after the 

 more volatile portions have passed over, the distillate throws down a 

 heavy yellow oil upon dilution with water, and somewhat later the 

 slightly acid aqueous distillate contains an abundance of the same 

 heavy oil in suspension. The quantity of oil which thus separates in 

 the course of distillation amounts to between three and four tenths of 

 one per cent of the crude wood spirit taken, although I am unable to 

 form even an approximate estimate of what proportion this may be of 

 the total amount present. 



The oil, as I received it, was feebly acid to test paper, and had a 



« N. Ann. Sci. Nat., xi. 24. 



