( 218 ) 



Usher and by Young, and supplement them by giving the variations 

 of the densities. 



After what the repetitions of de Heen's experiments had taught 

 us again about the asserted differences of density at the same pres- 

 sure and the same temperature above the critical temperature, our 

 repetition of Teichner's experiments has become rather a first con- 

 tribution to the study of the variations of density with temperature 

 and pressure by this way, than a refutation of the conclusions 

 derived from Teichner's experiments. We have, however, been able 

 to show sufficiently by our experiments that these conclusions are 

 erroneous. 



§ 2. Repetition of one of de Heen's experiments. As we can refer 

 to Comm. n°. 68 with regard to the choice of the experiment which 

 is to be repeated (on account of the systematic character of the 

 deviations only one need be repeated), and as on another occasion 

 a full description of the apparatus used and the different operations will 

 be given, we think that the following remarks on the arrangement 

 of the experiments will suffice here. 



1. The pure carbonic acid was prepared by distillation. The 

 admixtures are to be estimated at no more than 0,00027 ( cf. 

 Keesom Comm. N°. 88 II, § 2 and V § 10 These Proc. Jan. 1904). In 

 the apparatus it comes into contact only with metal, glass, and cork 

 ''packings of this gave a perfect closure after having been repeatedly 

 tightened during a week.). 



2. The apparatus, the conduits, and the further auxiliary arran- 

 gements, among which also two metal bottles with the purified 

 CO,, are all in connection with a mercury airpump. One of the 

 bottles with pure CO, serves for rinsing. From the second the 

 desired quantity is conveyed into the apparatus by distillation. 



3. The density in every reservoir is determined by making 

 the carbonic acid flow from it into a large reservoir with mercury 

 manometer kept at constant temperature. In the volumenometric 

 calculations the corrections are applied according to the empiric 

 equation of state V s. 1 of Comm. n°. 74 (Arch. Néerl. (2) 6, 

 1901). Errors in the density caused by leakages in the reservoirs 

 at high pressure are excluded. It was ascertained by separate 

 control experiments that the total amount of CO, in the apparatus 

 remained unchanged during the experiments. 



4. The apparatus was kept at uniform constant temperature by 

 means of flowing water, a xylene thermoregulator (see Comm. N°. 70 

 III § 3 These Proc. May 1901) and a valve stirrer (see Comm. 



