500 Researches on the Elementary Law of II 'ydrodi fusion, 



that time forth varied, with increasing time, in the form of a 

 simple geometrical progression, 



kt 



If we calculate by aid of this latter relation the value of the 

 constant 77 = ^ k from all the observations of each two conse- 

 cutive days according to the method of least squares, we find 

 from the observations of 



13th & 14th Nov. v= 0*2032 

 77=0-2066 

 97=0-2045 

 97 = 0-2027 

 ^ = 0-2027 

 97=0-2049 

 97=0-2049 



14th „ 15th 

 15th „ 16th 

 16th „ 17th 

 17th „ 18th 

 18th „ 19th 

 19th „ 20th 



Mean 

 temperature. 



. 9-6 



. 9-5 



. 9-5 



. 9-5 



. 9-5 



. 9-5 



. 9-4 



The mean values from the first four, the last four, and from 

 all these values are: — 



97 = 0-2042 

 97 = 0-2038 

 97=0-2042 



Certainly these numbers scarcely permit a doubt to arise 

 about this, that the quantity which according to the theory 

 should be constant was in fact constant for the experiment- 

 conditions here realized. Fick's elementary law is, accord- 

 ingly, for those differences of concentration which were present 

 in the diffusion-vessel from the fourth day, indeed the exact 

 expression of the progress of the diffusion. 



From the above mean value for 97: 



7T 



T 2 k, and the value of 



L (2*99 centims.), the following is found as the value of Fick's 

 diffusion-constant : — 



k= 0*1849 — , 1 * - , valid for the mean temperature 9°*5. 



[To be continued.] 



