Valency of the Radio elements. 



399 



Fig. 1. 



In the experiments with the extremely dilute solutions dealt 

 with in the work to be described, since no difficulty on 

 account of incomplete dissociation could arise. 



The apparatus shown in fig. 1 is essentially a copy of 

 Scheffer's. The lower part is filled with 3 x 16*05 c.c. of 



water, and the liquid under examination 

 is allowed to flow into it from a pipette 

 16*05 c.c. in volume. Experiments with 

 KMn0 4 solution showed that a sharply 

 defined surface formed between the 

 heavy liquid which had flowed in from 

 the pipette, and the light liquid already 

 contained in the vessel. 



When diffusion has taken place and 

 the experiment is finished, the pipette is 

 filled with some heavy liquid such as 

 chloroform, or a saturated solution of 

 calcium chloride, and the liquid allowed 

 to flow in very slowly while an equal 

 volume of the diffused liquid is forced 

 out of the apparatus at A. This gives 

 layer I. By repeating- this operation, 

 layers II., III., and IV. are obtained, 

 and then analysed. As a rule only 

 layers I. and II. were investigated. 

 The height of the layers was measured 

 with a cathetometer, and found to be 

 1*510 cm. 

 A heavy block of lead was attached to the glass apparatus 

 and the whole immersed in a large water-bath in an under- 

 ground room, the temperature of which did not vary more 

 than about 0°*1 C. during an experiment. The diffusion 

 coefficient of noimal hydrochloric acid solution determined 

 with the apparatus described above was at 15 D *2, 2*29 sq. cm. 

 per day, which by calculation gives at 18°, 2*48. The 

 values obtained by Arrhenins and Scheffer are 2'40 and 

 2*48 at 18° respectively. All values determined in these 

 experiments were reduced to 18°, a temperature coefficient 

 of 2'6 per cent, per degree being assumed. This is the value 

 obtained theoretically by Nernst*, and experimentally by 

 Schuhmeister f , Long J, Weber §, and others. 



* Zeit.phys. Chem. vol. ii. p. 624 (1888). 

 t Wien. Ber. vol. lxxix. p. 603 (1879). 

 t Wied. Ann. vol. ix. p. 6L f ; (1880). 

 § Wied. Ann. vol. vii. p. 469 (1879) 



2 E 2 



