3f>2 



viscosity of butane at this temperature .0001005. In order to com- 

 pare tiie two results at t = .809 we have calculated for these 

 vapours the constant ?n^ ^^^^' ^k""''" pk'l^, which Kamerlingh Onnes ') 

 has given for liquids. For comparison we have added the values 

 calculated for methyl chloride, benzene and nitrous oxide, with data 

 taken from Landolt's Tables (4th edition). 



X107 T M Tk /)k yi/'/aTk Vepk^'a /-W27'k Vk^/a 



1005 343.1° 58.08 423.9 37-5 



885.1 373.1° 72.10 460.9 32.9 



1082 366.6° 50.48 416.1 66.0 



1249 455.0° 78.05 562.4 47.9 



1342 249.6° 44.02 308.5 75.0 



The agreement as regards the hydrocarbons is not so near as for 

 the liquids. For the rest the numbers do not diverge more than for 

 the liquids, the data for which are given below for comparison. In 

 the computation we have used for butane ^) our own determination, 

 for the saturated hydrocarbons the data of Thorpe and Rodger'), 

 for the remaining substances the figures given by M. de Haas^). 



1) Gomm. Leiden SuppL 23, p. 85. 



2) Gomm. Leiden, 136. 



8) Thorpe and Rodger, Phil. Trans, 185A; 440; 1894. 

 -i) Gomm. Leiden 12, p. 12; 1894. 



