112 C. E. Linebarger — Apparatus for the Rafid 



larger tube, these vapors rise and heat the inner tube with its 

 contents to a desired constant temperature for any length of 

 time. 



III. Method of Making a Determination. 



The first thing to do in using the apparatus is to get the 

 lower extremities of the two capillary tubes at the same level. 

 This may be accomplished in the following simple manner. 

 A spirit-level is placed upon a piece of plate glass, which in 

 turn is set upon the support H at the required height, and 

 levelled. The pointers of the side-scale, as well as of that on 

 the screw head, are set at zero, the tubes allowed to rest freely 

 upon the plate glass, and then clamped in position. While 

 this way of fixing the tubes answers well enough for the initial 

 adjustment of the apparatus, it is not sufficiently accurate to 

 insure their being replaced in the same position, if, from any 

 cause, they become displaced. Indeed, it is not at all certain 

 that the tubes are at the same level to within 0*1 °^°', when 

 adjusted in the above manner ; yet this degree of accuracy is 

 entirely sufficient for the first adjustment, and by the use of a 

 standard liquid it will be shown how they can afterwards be 

 gotten into the same position to within 0*01 °''^. 



The test-tube has a mark scratched on its side, which indi- 

 cates the volume of liquid that is to be taken for a determi- 

 nation of its capillary constant, it having been found that 

 differences in the distance between the surface of the liquid 

 and the orifices of the tubes have some influence upon the 

 readings of the instrument.* The volume of the liquid may 

 be as small as a couple of cubic centimeters, if a small test- 

 tube be used ; generally, however, it is advisable to employ 

 from five to ten cubic centimeters. The test-tube is filled with 

 the liquid under examination to this mark and the tube sus- 

 pended in the bath. The beaker is placed upon a piece of 

 asbestos board or wire gauze, set upon the retort ring, which is 

 raised until the capillary tubes are close to the bottom of the 

 test-tube. A thermometer is introduced into the liquid, and 

 the bath-liquid stirred, so as to insure uniformity of tempera- 

 ture. The mode of procedure is essentially the same when 

 a vapor jacket is employed. The rapidity with which the 

 liquid undergoing investigation takes on the temperature of 

 the bath may be hastened by blowing bubbles up through it 

 by compression of the air in the rubber ball K. 



When the temperature of the liquid is the same as that of 



* This influence is, however, but slight. Readings with ether were found to 

 differ by only -^\-^ of an inch, when the differences between the free surface of 

 the liquid and the lower extremities of the capillary tubes differed by more than 

 four inches. 



