COAL-TAR AjSTD WATEE-GAS TAE CREOSOTES. 29 



The flask in position for distillation is supported on an asbestos 

 board in which a hole has been cut almost as large as the great 

 diameter of the bulb. The outline of this opening is irregular to per- 

 mit the flame to play about the bulb. No wire gauze is used, for 

 there is no danger of breakage so long as the flame does not come in 

 contact with dry glass. The portion of the bulb above the asbestos 

 board and below the Hempel column is protected from drafts by an 

 asbestos box. No protection is given to the Hempel column unless 

 the condensation becomes so great that the column begins to fill, and 

 then it is surrounded by an asbestos box sufficiently large to prevent 

 any portion of it coming in contact with the glass. The condensers 

 used are ordinary glass tubing about one-half inch in diameter, 

 drawn down at one end to about one-fourth inch and flanged at the 

 other to receive a cork stopper. The length is approximately 8 

 inches. This has been found to be sufficient to condense all of the 

 lighter oils but not sufficiently long to cause much solidification of 

 the higher distillates in the tube. If solidification should occur, it is 

 always melted out before the fraction is taken. 



The thermometers used in this work were made of Jena borosilicon 

 glass and were filled above the mercury column with carbon dioxide 

 at a pressure of approximately 15 atmospheres. They read from 180" 

 to 550° C. and were standardized either by the Bureau of Standards 

 or by the German Physikalisch Technische Reichsanstalt. Correc- 

 tions were made for the slight inaccuracy of the thermometers and 

 also for the emergent stems. This latter correction is not usually 

 made in creosote distillation, and would not be necessary if a standard 

 thermometer were used for all such distillations and if the length of 

 the emergent stem were the same in all cases. At the time this work 

 was started no standard theremomter for creosote distillation had 

 been adopted or even proposed by the various associations interested 

 in wood preservation. The correction was necessary, therefore, as 

 only by this method could the data here presented be compared with 

 data in the collection of which thermometers of different lengths had 

 been used. 



For those who are not familiar with the emergentstem correction, 

 the following explanation of its meaning and use is given. Mercurial 

 thermometers are usually standardized with the whole of their 

 mercury column at the same temperature as that of the bulb. This 

 is possible only when the total length of the thermometer is bathed 

 in the heated vapors or liquid. If this is impossible, then the thread 

 of mercury is cooler than the bulb, and an error is introduced which 

 makes the observed reading too low. If the difference between the 

 temperature of the stem and bulb is small, this error is negligible; 

 but if the difference is large, and the length of the emergent stem is 

 great, the error becomes a factor of considerable importance, and 



