672 



mentioned in § 3 yielded varying values in contrast to those of 

 aniline and of p-toluidine, aa will appear in ^ 8. For the qnantily of 

 carbonic acid which combines with one molecule of m-toluidline, was 

 found successively 0.76, 0.79. 0.85, 0.86, 0.88, 0.88, 0.93, 0.89, 

 0.86, 0.92, and 0.89 mol. These values for the carbonic acid content 

 are most probably all too small. The cause of this deviation is in 

 my opinion the following: Liquid carbonic acid and m-toluidine are 

 little miscible. Accordingly the foi'ination of the compound on cooling 

 takes chietly place on the boundary of the two layers. In consequence 

 of this a partition of solid substance is continually formed, separating 

 the two layers. Part of the (oluidine can, therefore, be withdrawn 

 from the action of carbonic acid. It is clear that after the excess of 

 carbonic acid has been sucked otf, the quantity of bound carbonic 

 acid is found too small. In order to render the formation as complete 

 as possible, the tubes were kept in ice for several days; in the 

 successive determinations this period increases from 2 to 10 days. 

 It ai)pears, therefore, that the time has not much influence on the 

 result of the analysis. In the last determination the tube was cooled 

 for 7 hours with ice and salt f — '15 to — 20°); it also yields too 

 low a result. The supposition that the m-toluidine should be impure, 

 appeared erroneous, as the correct value of 65° was found for the 

 melting-point of the acete compound. I think I am justified in 

 concluding from the above-mentioned determinations that the compound 

 likewise consists of equal molecular quantities of toluidine and 

 carbonic acid. 



7. The system p^ohciclme-carbonic acid; the p-tolylcarbaminic acid. 



In the P-T-diagram the system p-toluidine-carbonic acid yields a 

 three-phase line LjLjG, which deviates little from that of the said 

 systems. (Cf. tig. 3). The quadruple point SLjLjG lies here at higher 

 temperature; the four three-phase lines which intersect in this 

 quadruple point, are indicated in fig. 3 ; the quantitative data in 

 table 4. The relative situation of the four phases is the same here 

 as in the preceding systems. The stable part of the three-phase line 

 SL,G terminates at low^er temperature in a second quadruple point 

 SSbL.G (Sb is solid p-toluidine). In the preceding systems the corre- 

 sponding quadruple point lies at lower temperature and pressure; in 

 this system the temperature of the two quadruple points differs little 

 from the critical temperature of carbonic acid. The three-phase lines 

 SL,G and SbL,G are easy to determine, when we heat at constant 

 pressure and read the temperature at which liquid is formed. 

 Without further examination we mav state about the three-phase 



