42 I Intelligence and Miscellaneous Articles. 



Daring the next four days (ma 1*014 gram) A sank to 7*712, 

 and then rose again. 



Meanwhile some cracks in the interior of the rod had come to 

 light : so that I broke off the observations ; but the results of this 

 one seriea are so remarkable that a further investigation of the pheno- 

 menon is desirable. — Wiedemann's Anncden, 1879, No. 10, (vol. viii.) 

 pp. 352-356. 



DETERMINATIONS OF THE VAPOUR-DENSITIES, AT HIGH TEMPE- 

 RATURES, OF SUBSTANCES THAT ATTACK MERCURY. BY L. 

 PFAUNDLER*. 



In connexion with the numerous newer methods for determining 

 vapour-densities, especially the most recent, by V. Meyer and C. 

 Meyer {Beibl. iii. p. 252), Pfaundler reminds us of one mentioned 

 already in 1870, in the Berichte desnaturwissenschaftlicJi-medicinischen 

 Vereins in Innsbruck. The construction of the apparatus he em- 

 ployed was substantially that of a Eegnault air-thermometer ; only, 

 instead of the simple glass cylinder, a glass vessel formed of several 

 compartments one above another, and connected by capillary tubes, 

 served for holding the vapour, by which the vapour to be investigated 

 could be kept separate from the mercury, at least during the obser- 

 vation. Moreover, in the case of dissociation, diffusion of the con- 

 stituents in unequal quantity can be prevented by employing a 

 capillary tube coiled in any manner instead of the second, third, &c. 

 compartments. The temperature is observed on an exactly like- 

 coustructed air-thermometer ; and the difference of pressure in the 

 latter and in the vapour-apparatus gives the pressure of the vapour 

 very accurately, since many errors eliminate one another. The 

 substance to be examined is introduced through a narrow tube into 

 the apparatus, which is then hermetically closed, the capacity of 

 the vessels having been previously determined in the known volumi- 

 nimetric manner. In the method used by V. and C. Meyer also, 

 the air (nitrogen &c. respectively) displaced by the vapour prevents 

 contact with the barrier-liquid ; the difference of principle between 

 the two methods, however, is this — that in the Meyers' the volume 

 of the vapour is deduced from that of the displaced air, while with 

 Pfaundler the determination has in view the measurement of the 

 pressure of the vapour at constant volume. Pfaundler himself 

 regards the Meyerian method as by far the simpler, while he con- 

 siders his own the more exact and hence more suitable for testing 

 theoretical relations. — Eth. in the Beibldtter zu den Annalen der 

 PhysiJc und Chemie, 1879, No. 7, p. 484-5. 



* Chem. Ber. xii. pp. 165-169 (1879). 



