296 



Intelligence and Miscellaneous Articles. 



of these Tables contain the salt-contents of the respective layers in 

 the diffusion-vessel for a series of values of a number dependent 

 on the coefficient and the duration of the diffusion. Given these 

 two quantities, the corresponding distribution of the salt is found 

 in the Tables. 



Conversely, with the aid of these Tables, the value of the diffusion- 

 coefficient belonging to each salt-content of a layer as given by 

 Graham can be found, and we can recognize, according to the 

 nature of the accordance or deviation of the coefficients resulting 

 from the data of one and the same experiment, whether the experi- 

 ment is in harmony with the theory or not. 



Diffusion-processes are very easily disturbed by currents pro- 

 duced in the liquid by differences of temperature, so that the upper 

 layers receive too much, and the deeper layers too little salt. The 

 results of Graham's experiments, however, may be more faulty still, 

 and in the same direction, in consequence of those currents which 

 can hardly be avoided when the liquid is drawn out with the siphon. 

 "We must therefore, even assuming that the theory accurately re- 

 presents the processes of diffusion, be prepared to expect considerable 

 differences between observation and calculation. Such differences 

 occur in many cases ; but there are also cases in which the devia- 

 tions are very slight. The following series give instances of the 

 close approximation that may exist between observation and 

 calculation : — 



Layer. 



I. 



II. 



III. 







Calc. 



"~Obs. 



Calc. 



Obs. 



Calc. 



3. 



3-284 



3-328 



5-392 



5-391 



2-936 



3004 



1-527 



1-482 



1-930 



1-928 



1-387 



1-369 



4. 



1-317 



1-290 



1-282 



1-287 



1-236 



1-225 



5. 



1-057 



1-073 



0-727 



0-751 



1-070 



1056 



6. 



0-850 



0-853 



0-376 



0-380 



0-876 



0-877 



7. 



0-640 



0-648 



0-170 



0-167 



0-700 



0-704 



8. 



0460 



0-469 



0071 



0-064 



0-542 



0-541 



9. 



0-318 



0-325 



0024 



0-021 



0403 



0-402 



10. 



0211 



0-215 



0011 



0-006 



0-289 



0-288 



11. 



0-134 



0-135 



0-005 



0-002 



0-204 



0-199 



12. 



0081 



0-082 



0003 



0001 



0-135 



0-133 



13. 



0-051 



0047 



0-002 





0-092 



0-086 



14. 



0-028 



0026 



0-002 





0058 



0055 



15. 



0-017 



0015 



0002 





0040 



0036 



16. 



0-013 



0011 



o-ooi 





0032 



028 



I. refers to an experiment with chloride of sodium, lasting seven 

 days, at the temperature of 9° 0. ; II. to an experiment with cane- 

 sugar, of six days' duration, at 9° ; III. to an experiment with a 

 mixture of the chlorides of potassium and sodium in equal parts, 

 of seven days' duration, and at 11-12° temperature. 



This Table shows that the mathematical treatment applied to 

 the diffusion-processes gives their course with very close approxi- 

 mation. 



