722 



taken from 658 — 600. The latter, obtained in the same way, indi- 

 cated a displacement from 750 — 600 in exactly 23.0 seconds. 



In order to derive in how mnch time this normal solution will 

 ionise from, 658 — 600, the ratio of the average sensibility of charge 

 of the distance 658—600 of the scale to that of 750—600 had to 

 be still defined. For this determination I made nse of a special 

 experiment taken very accurately and which was of equal import- 

 ance for the calculation of all the other samples. This consisted in 

 examining the ionisation of a substance of which the ionisation was 

 hot too small, from scale-division 750 — 600, and that in such a way, 

 that the time was continually checked which was wanted for passing 

 through 10 scale-divisions. The values in seconds amounted from 750 to : 



tirst determination: 21, 23, 24, 20, 22, 31, 24, 20, 24, 29, 32, 

 27, 3J, 33, 34. 

 ^'- second determination: 31, 27, 29, 21, 25, 25, 29, 26, 30, 25, 36, 



34, 34, 28, 28. 



From this follows that the charge wanted to displace the needle 



from 658 — 600 amounted to 180/411 of the value, which applies to 



parts of the scale 750 — 600. Then the real ionisation time of the 



normal solution for 658—600 was: 180/411 X 23 sec. = 10.1 sec. 



Consequently the sample was 416/10.1^41.2 times weaker than 



the other, so that every gramme of the sample contained: 



1.25 X 10-10 



— ;; — — — = 0.61 >; 10-12 grammes of radium. In this way the 



values for the radio-activity of every sample of part I have been 

 derived ^). 



1) The calculation might yet be executed somewhat differently and that with the 



aid of ionisation values of only 100 scale-divisions, e.g. of 750—650, and this 



for a natural leak, emanation as well as for normal solutions, for from the data 



as given above follows (cf. b) that the substance ionises from 750—650 on an 



average in 4 min. 16 sec. or 256 sec, whereas the natural leak (cf. a) ionises 



over the same space in 7 min. 40 sec. of 460 sec. From which follows that the 



natural leak together with that of the emanation would ionise in 460 sec. 



460 , ^ . 



-r^ = 1.8 time over that part of the scale, (only suppose for the calculation of 



the sensibility of charge constant from 750—650), so only the emanation 0.8 time 



over that part mentioned in that time. For the final calculation we then derive 



from c, that the normal solution, that ionises in 23.0 sec. from 750 — 600, displaces 



253 

 the needle from 750—650 in 7-prX 23 sec. = 14.1 sec, consequently in 460 sec. 



460 .. . 



— — — 32.6 times ionises over the division of the scale mentioned. Finally there 



follows from all this that the activity of the normal solution is — — — 40.8 times 



