456 Messrs. C. H. Bosanquet and H. Hartley: Notes 



and electron. Some of these combine with electron to give 

 strongly polar substances like the alkali metals, in the same 

 way as the radicle ammonium combines with chlorine to 

 give the strong electrolyte ammonium chloride. Others on 

 combination with electron give non-polar substances such as 

 neon, just as the radicle phenyl when united to chlorine 

 gives the non-electrolyte ohlorobenzene. 



(3) Werner classified simple binary compounds like 

 potassium chloride and platinic chloride as compounds of the 

 first order, combinations of such compounds of the first 

 order, potassium platinichloride for example, being designated 

 compounds of a higher order. 



Since the substances known as the chemical elements are 

 the simplest combinations of proton and electron which are 

 capable of separate and independent existence, it follows that 

 the chemical elements are the true compounds of the first 

 order, Werner's compounds of the first order being really of 

 the second order, and bodies like potassium platinichloride, 

 of the third order. 



(4) Co-ordination is involved in all valency phenomena. 



LII. Notes on the Angle of Contact. By 0. H. Bosanquet, 

 Brakenbury Scholar, Balliol College, and Harold Hartley, 



Fellow of Balliol College, Oxford*. 



IN spite of the importance of the angle of contact both in 

 the theory of surface tension and in its measurement, 

 our knowledge of this physical constant is scanty and un- 

 reliable. 



It is still uncertain whether all liquids which wet glass 

 have a zero angle of contact or notf- For instance, Magie 

 (Phil. Mag. xxvi. p. 162, 1888) found a zero angle of con- 

 tact for a number of organic liquids, and a small finite acute 

 angle of contact for acetic acid, turpentine, petroleum, and 

 ether, but his method did not admit of great precision. 

 Again, the existence of such small angles of contact has been 

 suggested as an explanation of the differences found for the 

 surface tension of liquids by various methods (e. g. capillary 

 rise, drop weight, and Jaeger's method). However, the case 

 of water has been carefully examined by Ramsay and Shields 



* Communicated by the Authors. 



t Since this paper was written a paper has appeared hy Richards and 

 Carver (J. A m. Chem. Soc. xliii. p. 827, 1921) describing- experiments 

 which show that the angle of contact is zero for liquids which wet glass, 

 if no evaporation is taking place. This conclusion is supported by the 

 results described here, which were obtained by a different method. 



