EXPEKIMENTAL METHODS. 11 



MATERIALS. 



The J. G. Newman Lumber Co., of Hattiesburg, Miss., furnished 

 for the experiments a large log of pitchy lightwood in which the pitch 

 was distributed with unusual evenness. From this log it was possible 

 to prepare a number of charges of chips, of which all from one portion 

 of the log were similar in resin content. 



PREPARATION OF MATERIAL. 



The method of selecting material so that each charge should be 

 comparable with the other, charges in the same group is shown in 

 Table 1 and figure 2. The sticks were sawed into sections at one 

 time, but usually the sections were chipped only as required; that is, 

 just before each distillation. Thus the sections for the last runs of a 

 group had been longer cut than those of the first runs, and although 

 they were kept in covered cans, or if without cover were piled close 

 together, there was still some chance of loss by volatilization, espe- 

 cially when some time intervened, as in the large number of runs in 

 Group I. To lessen the loss by volatilization during the chipping 

 process, the chips were covered with water as fast as they were made. 

 The sawdust charges were put into the retort without any delay after 

 collection, except in runs 2 and 3, which were prepared and collected 

 but not distilled at the same time with run 1. 



DISTILLATION. 



Only a brief description of the procedure needs be given here. The 

 same general methods were used in all cases and the details are given 

 later in the tabulated record of the runs. 



REGULATION. 



The speed and pressure of the distillations were regulated simply 

 by the inlet valve at the bottom and by the outlet valve at the top of 

 the retort. During distillation at atmospheric pressure the outlet valve 

 was left open and the speed regulated by the inlet valve alone; but 

 during distillation at higher pressure it was, of course, necessary to 

 use both valves in order to keep both speed and pressure at the 

 required values. The variation in speed was never more than one- 

 half minute per liter of distillate, and in pressure never more than 

 2 pounds per square inch from the required values. 



