( 271 ) 



but yet these observations seemed important enough to us to com- 

 municate something about them ^). 



The ari-angement for the filUng with cai'bonic acid was tlie same 

 as that used in our former experiments ; the nitro-benzene could not 

 be conveyed quantitatively in the same way as we followed for urethane 

 i. e. in solid state. For greater quantities this could be done in small 

 bulbs fused together, placed in a pear-shaped apparatus, which was 

 fused to tlie capillary of a Cailletet-tube. For smaller quantities it 

 appeared to be unfeasible to make the bulbs small enough and till 

 them, and to convey in this way a quantity of some mg. quan- 

 titatively into the tube. For this purpose we have used very narrow 

 glass capillai-y tubes; the extremities were drawn out still further to 

 an exceedingly small diameter. These tubes, open on either side, 

 filled themselves when one end was im merged in the liquid, by tlie 

 influence of the capillary pressure. They were not closed because the 

 liquid appeared to char by the high degree of heating required for 

 this. Moreover it proved to be unnecessary to close them ; it appeared 

 to be impossible to ascertain any loss of weight, even after they had 

 been for some time in a space which had been exhausted by means 

 of the Gaede-pump. By cautious heating of the filling apparatus, the 

 liquid was expelled from the tube, after the whole space had been 

 exhausted of air, and fused to, and the drop was conveyed from the 

 filling-apparatus into the Cailletet-tube, which had already been placed 

 in the pressure cylindre, provided with a stirrer. 



Then the tilling-apparatus was cut off, and the capillary of the 

 tube was fused to the glass capillary, which was attached to the 

 steel capillary of the high pressure cock by means of sealing wax, 

 so that then the carbonic acid could be added. 



In our foregoing communication we could praise our tubes of 

 borosilicate glass, but a new supply of this kind of glass, which we 

 had to use now, pi-oved very unsatisfactory. At least some ten tubes 

 burst during the experiment, both under the influence of the pressiu-e 

 and luider the influence of local heating during the preparation of 

 the tubes or of cooling during the filling. Hence the occurrence of so 

 many gaps in the observations given by us. Of many mixtures with 

 concentrations between those given by us e.g. witli a; = + 0,01, 

 0,004, 0,003, it could only be stated that the required concentration 

 had not been reached, but definite observations could not be made, 

 because the tube burst. We passed at once to another concentration 



1) Our attention was drawn to this sy£;tein by the communication of Büchner 

 (Diss. Amsterdam 1911 p. Ii2t2} about the unmixing of mixtures of nitrobenzene 

 and carbonic acid. 



19 



Proceedings Royal Acad. Amsterdam. Vol. XIV. 



