708 



iiniïiei'sed in the water; only the bent point D, in wiiich there is 

 no mercury during the measurements, projects above the water. By 

 means of a water-jet air pump the water from the glass tube is 

 sucked up, and conveyed to the mixing vessel, in the same w^ay as 

 the mercury is sucked up and thrown over (by air being sucked 

 up at the same time) in the well-known Kahlbaum air pump. The 

 water from the mixing vessel flows or its own accord to the thermo- 

 stat through the connection at the bottom, which secures a strong 

 water current. Thus the required accuracy, at the utmost 0°.l, 

 is easily obtained. Eventual variations in temperature can be taken 

 into account, when the weight of the total quantity of mercury in 

 the two tubes is known. This quantity is every time determined by 

 pressing the remaining mercury from the tubes and weighing it 

 when the last reservoir has been gauged. As a rule the temperature 

 variations were not worth mentioning, and it was not necessary to 

 apply temperature corrections. 



When a measuring tube must be cleaned on account of conta- 

 minations, a piece may every time be knocked off at the top. After 

 the cleaning the tube is fused to at the next line. This can be done 

 so accurately, and the capillary is so narrow here, that it may be 

 assumed that the volume of the tube is diminished by the known 

 volume between the lines. 



It is unnecessary to apply more than ten lines. After so many 

 cleanings, the volume wire is damaged as a rule, if the tube was 

 not broken before, and to repair the volume wire is very difficult. A 

 newly wrapped tube is, indeed, always rubbed with zapon lac, but 

 in the long run this measure is no safeguard for the thin volume wire. 



That in this way an exceedingly accurate calibration is obtained, 

 may ajipear from the following example. The values give the total 

 volumes from the upper end of the tube to the different places of 

 contact at two different calibrations. 



7.0561 

 7.4276 

 8.0137 

 8.8849 

 11.5623 

 14.9740 



7.0554 

 7.4281 

 8.0121 

 8.8843 

 11.5595 

 14.9709 



20.0667 

 25.0062 

 34.5016 

 43.7536 

 85.4267 

 87.5029 

 90.3264 



20.0590 

 25.0078 

 34.5005 

 43.7516 

 85.4287 

 87.5008 

 90.3269 



