( 542 ) - 



(los('i-il)O(l l)v K \MKin,iN(iii Onnks jind Hvndman. tlio (Icfoi-niiiialioii 

 of llie couiprcssiUilitv of' ciirlxui dioxide niid some iiiixliires of' carbon 

 dioxide and oxygen at oi'diiiary pressur-es, togefliei' \\\i\\ the resnifs. 



§ '2. llii' siihsfiiiiccs. To obtain the earl)on dioxide I used the 

 method followed in the Pliysical Laboratoi'v at Leiden ^), which 

 together with the inijirovenients made in the last ^'ears will be 

 described in a }>aper on the aj)j)aratns and methods used in the 

 Cryogenic Laboi-atory. 



The pnrify of tlie carbon dioxide tlins obtained a[)pears from the 

 increase of the |)ressui'e at the condensation at 25". 5 ('. which amounts 

 to only 0.07 aim. 



The oxygen was prepared fi-om potassium j)ei-nianganatc in the 

 way desci-il)ed in ('omm. N". 78, These Proc. I \'. April 1902. p. 7(58. 



§ 3. Tlir jn-i'itarntloi} of flw nii.i'fiires, tlw (li'U'fiiiiiKition of flu' cuni- 

 position iiixl the compres.sihiJitii of the nn. tin res <it onlntarj/ pre.-isiirt's. 

 For the prei)aration of tiie mixtures I had at my disposal the apj»a- 

 rafus desci-ibed in Comm. N". 84, These Proc. \', March 1903, § 21. As 

 the operations recpiired foi" the preparation of a mixture of accui-ately 

 known composilif)n ai'e descril)ed there, I need not eidarge here on 

 the details of this subject. I shall oidy mention that the apj)aratns was 

 connected by means of the cock i\^ (see j)late 11 of that paper) to 

 the apparatus for the ])reparation of oxygeii, by means of cock r.^ 

 to the carbon dioxide reservoir, before whi(di (here was a drying- 

 tube tilled with phosphorous penfoxide, and also to the experimental 

 tid»e that had to be filled. After the uuxtui-e had been ju-e|)ared, 1 

 have in\-estigated in the Noliimeuometer A' the deviation from the law 

 of BoYi.K, in order to be able to express Ihe volumes of my mixture 

 at high pressures in terms of the theoretical normal volume. Although 



1 

 for my investigation an accuracy of ..^^^ would have been sufficient, 



1 have gone a little fui-fher because in itself the knowledge of the 

 deviations from the law of Boyt.k at ordinary pressures is important and 

 the apparatus without difficulty admits of a higher degree of accu- 



1 



racv. Taking all possible precautions an accuracv oi , , , ^ might 



be reached. Yet I w^as satisfied with an accui-acy of . To judge 



-^ 5000 ■' ^ 



of this the following may serve : 



') Conip. among otliors Kuenen, Arcli. Néeil. t. XXVI, p. 3 and V^erschaffelt 

 Ziltlugsversl. Juni '95, Comm. N". 18, Leiden. 



