96 BULLETIIS: 1036, U. S. DEPAETMEXT OF AGRICULTURE. 



of the bulb one-half inch from the surface of the oil in the retort. The exact location 

 of the thermometer bulb shall be determined by placing a vertical rule graduated in 

 divisions not exceeding one-sixteenth inch liack of the retort when the latter is in 

 position for the test, and sighting the level of the liquid and the point for the bottom 

 of the thermometer bulb. The distance from the bulb of the thermometer to the 

 outlet end of the condenser tube shall be not more than 24 or less than 20 inches. 

 The bm-ner should be protected from drafts by a suitable shield or chimney. 



Exactly 100 g. of oil shall be weighed into the retort, the apparatus assembled, and 

 heat applied. The distillation shall be conducted at the rate of at least one drop and 

 not more than two drops per second, and the distillate collected in weighed receivers. 

 The condenser tube shall ])e warmed whenever necessary to prevent accumulation 

 of solid distillates. Fractions shall be collected at the following points: 210°, 235°. 

 270°, 315°, and 355° C. The receivers shall be changed as the mercury passes the 

 di^dding temperature for each fraction. When the temperature reaches 355°, the 

 flame shall be removed from the retort, and any oil which has condensed in the off- 

 take shall be drained in the 355° fraction. 



The residue shall remain in the retort with the cork and the thermometer in position 

 until no vapors are visible; it shall then be weighed. If the residue is to be further 

 tested, it shall then be poured directly into the brass collar used in the float test, or 

 into a tin box, and covered and allowed to cool to air temperature. If the residue 

 becomes so cool that it can not be poured readily from the retort, it shall be reheated 

 by holding the bulb of the retort in hot water or steam, and not by the application 

 of flame. 



For weighing the receivers and fractions, a lialance accurate to at least 0.05 g. shall 

 be used. 



During the progress of the distillation the thermometer shall remain in its original 

 position. No correction shall be made for the emergent stem of the thermometer. 



When any measurable amount of water is present in the distillate it shall be 

 separated as nearly as possible and reported separately, all results being calculated 

 on a basis of dry oil. When more than 2 per cent of water is present, water-free oil 

 shall be obtained by separately distilling a larger quantity of oil, returning to the oil 

 any oil earned over with the water, and using dried oil for the final distillation. 



A more refined test, in whicli the Hempel flasls: is used, is given in 

 Part II. 



MOISTURE IN CREOSOTE TEST. 



It sometimes happens that it is necessary to make a determina- 

 tion of the moistures in creosote. If the moisture content is small 

 (less than 2 per cent), this can readily be done in conjunction with 

 the distillation test. If, however, the water exceeds 2 per cent, or 

 if there is difficulty in carr3ring out the distillation test on account of 

 the spattering, the following method should be used. It has been 

 adopted as standard by the American Wood Preservers' Association, 

 the American Railway Engineering Association, and the American 

 Society for Testing Materials. 



Still. — A vertical, cylindrical copper still with removable flanged top and yoke of 

 the form and approximate dimensions shown in figure 46 shall be used. 



Thermometer. — The standard distillation thermometer as specified under ''Distil- 

 lation," shall be used. 



