596 Dr. (x. Hevesy on the Diffusion and 



Diffusion of thorium B into 1/12 N ammonia. 



D150.8. Digo. 



!• T^H °' 37 °' 39 



n - lUk °' 37 °- 36 



IV. r^ 0-34 0-36 



Mean value for D 18 o is 0'37 sq. cm. per day. 

 Diffusion o£ thorium B into 1/14 N ammonia. 



Di5o. 6 . Disc 



L i« 0>39 °' 41 



IL HW °- 32 °' 34 



Mean value for Di 8 o is 0'37 sq. cm. per clay. 



Radium F, thorium B, and (as shown by a qualitative 

 experiment), radium E also thus diffuse substantially more 

 slowly in alkaline than in acid solution. They are there- 

 fore, in a great degree, present in alkaline solution in a 

 colloidal form. 



The diffusion constants found above are considerably 

 smaller than those obtained for colloidal albumen and 

 similar substances. However, it is not to be expected that 

 in such extreme dilution as that of the material present in 

 these solutions of radio-elements large particles would be 

 formed. Moreover, similar diffusion constants were obtained 

 in the case of colloidal gold solutions by Whitney and Blake * 

 as well as by Svedbergf. An attempt to estimate the size 

 of these colloidal particles of radium F and thorium B can 

 be made by using the equation D 2 M = 60. Substituting the 

 different values of D in the various cases, one obtains in the 

 first case an average value for the molecular weight of 1600 

 corresponding to an aggregate of 8 atoms, and in the second 

 case a value of 460 corresponding to an aggregate of only 

 two atoms. 



Diffusion in Neutral and dilute!?/ Acid Solutions. 

 Traube-Menganini and Scala have demonstrated the 

 direct formation of colloidal metallic solutions by the bring- 

 ing together of such metals as nickel, tin, etc., and distilled 

 water, and then this colloidal metal is transformed under 



* Whitney & Blake, J. Amer. Chem. Soc. xxvi. p. 1363 (1904). 

 t Svedberg, Zeit. jrfiys. Chem. lxxiv. 



