354 



viscosity of lieliiiiii and livdrogeii (comp. H Kamerlingh Onnes and 

 SoPHUS Wkbkr; Comm. N". 134). 1 have tlierefoie tried, whether an 

 improveinerit is not brought abont - as appeared to be the case in 



K /T 



Comm. N". 134 — bj nsing a formula of the form — - = 



As shown by column IV |i =r 5 gives a very good agreement. 

 According to Maxwp:tj/s theory in a more general form '), where 

 the forces between the molecules ai-e taken pro|)ortional to ?•-", we 

 should have to take for neon 2 |:? r 1 =^7i=z\\. 



The measurements give for Ihe temperature-coefficient between 

 0° and 100° C, ,^(,_ioii, 0.00226; this agrees very closely with the 

 temperature-coellicient of the viscosity , for which RANKiNE'jfoundO.00225. 



§ 5. From the eK|)erinieiilal \aiues of // and the corresponding 

 pressures p the values of Z>'™,, and y, can be determined according 



to the relation D'.on — D'l 1 + " )• In this manner the following 

 results for y^ were obtained : 



The values found for D'ror, «ii'e given in the 5''' column in 



the tables on p. 350 and p. 351. In the tables for 0° and 



100° C. D\.on. will be found to become too small below about 



y> = 4 cm.; this is quite intelligible seeing that the theory about the 



lemperal ure-drop is derived under the a8Sum|)tion that the mean 



free path ?. is small compared lo the dimensions of the apparatus. 



For neon at 0° C. and /> = 4 cm. / = 0,000375 cm., 2r, the 



diameter of the experimental wire being 0,0005240 cm., hence 



2r 



— =1,4. It appears therefore that the theory for the temperature- 



di-op given by Kundt, Wakbukg and Smot.hchowski is applicable 



1) S. Chapman. London Phil. Trans. A. 211, (1912), p. 433 and 216, (1916), 

 p. 279. 



3) A. 0. Rankine. Physik. Z. S. 11 (1910) p. 497 and 745. 



