069 



phase tension \jJj,G begins to depart more from the carbonic acid 

 tension with increasing temperature; at the quadruple point the 

 deviation amounts almost to 2 atmospheres; at the critical point of 

 carbonic acid to abont 37, atmospheres. 



It follows from the already mentioned quadrnple rule, which 1 

 formulated before as follows: The region that does not possess metastable 

 j)rolongations of threephase lines in the P.-T.-projection, is that of 

 coexistences of phases of consecutive concentration •), that the region 

 between SLjG and SL,L, satisfies the above mentioned condition. 

 In this region, which besides by the two mentioned three-phase 

 equilibi'ia is also bounded by SL^G and LiL,G resp. by SLiL, and 

 SL,G, the coexistences occur of the two phases which the adjoining 

 three-phase equilibria have in common, hence in this case S -f- ^i, 

 Lj -f- G, and S -\- L^. As these coexistences according to the rule 

 mentioned must refer to phases which succeed each other in con- 

 centration, the succession is GLjSL, ; the concentration of the com- 

 pound lies, therefore, between that of the two coexisting liquid 

 layers. Hence the transformation S ^ Lj -f- L, takes place on the 

 three-phase line SLiL, in the neighbourhood of the quadruple point. 



3. In order to get acquainted with the concentration of the 

 compound Dr. Polak has caused a weighed quantity of aniline to 

 act on an excess of carbonic acid in a fused-to tube at the ordinary 

 temperature. After the compound had been formed the tube was 

 opened again at —80°, and placed in a bath of about — 60°; after 

 half an hour the tube was again fused to, and weighed after having 

 been heated to the ordinary temperature. This analysis yielded the 

 concentration C,H,NH, . 1 . 01 CO,. 



I have carried out three analyses in a way that differs but little 

 from that described here; the method of investigation was the same 

 as that which 1 have described in my second paper on the system 

 sulphuretted hyd rogen- water ^"l ; the excess of carbonic acid was 

 sucked off at — 80^ by means of a waterjet pump. For the quantity 

 of carbonic acid in gramme-molecules which combines with one mol. 

 of aniline, was found successively 0.98, 0.99, and 0.98. The compound 

 consists, therefore, of an" equal number of molecules of aniline and 

 carbonic acid. 



4. The sijsteui o-toluidin-carbonic acid; the o-to/i/l-rarhaw.inic acid. 

 Also in the system o-toluidine-carbonic acid I have been able (o as- 

 certain the formation of a compound ; the quadruple point lies here, 



') loc. cit. 

 ') loc. cit. 



