236 AiSTNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



made upon flames b}'' Moi*eau,^ Lusby,^ H, A. Wilson, and others.^ 

 The negative ions in flames appear to differ little from corpuscles 

 and are scarcely loaded in their accidental encounters with molecules. 

 The positive ion has a size of the order of magnitude of a free atom- 

 ion and often appears to be formed of an hydrogen atom, more rarely 

 of a metallic atom in certain flames colored by salts. 



(3) It is mostly with ionization at ordinary temperatures that the 

 newer results have been obtained. The study of ionized gaseous 

 mixtures was first undertaken by Blanc * and by Wellisch.^ Accord- 

 ing to them an ion produced in a gas A and then transported into 

 another gas B, assumes a mobility characteristic of the gas B. This 

 agrees with the idea of temporary agglomerations constantly de- 

 stroyed and built up again. Blanc carried out his experiment with 

 ions formed in carbonic acid gas and then transported into air. 

 Wellisch created his ions in CH3I of CCI4 and then transported them 

 into hydrogen. According to him the ionization in hydrogen is 

 enormously increased by traces of CH^I whereas the mobility changes 

 only slightly. It looks as if the heavily ionized molecules of CH3I 

 transfer their charges to the hydrogen molecules. This is a re- 

 markable property belonging to certain ions. The same experi- 

 menters, as well as Lathey,** Tyndall,'^ and others, have studied 

 with precision the influence of traces of a foreign gas upon the 

 mobility of ions. According to Blanc a small amount of aqueous 

 vapor diminishes the mobility of the negative ion and increases that 

 of the positive ion in air and in carbonic acid gas (450 and 490 

 C. G. S. for air instead of 380 and 600). The same occurs with 

 alcohol vapor. The molecules of water and alcohol without doubt 

 remain longer associated with the charged nucleus than those of 

 air, carbonic acid gas. or hydrogen. Just the opposite is the case 

 with the molecules of CH3I, CCI4, etc. From this we see also that 

 in certain gases the positive ions finally surpass the negative ions 

 in mobility. This, for instance, happen with chlorine. 



The most remarkable fact in this connection was noted by Franck.^ 

 Working upon argon he found normal mobilities (of the order of 

 1 cm. in a 1 volt-cm. field) for the positive ions, while the negative 

 ions had mobilities of more than 200 cm. and behaved as corj)uscles 

 free from corteges of molecules during tlie major part of their 

 courses in the gas. This enormous mobility diminishes very rapidly 



iMoreau, Comptes Rendus, vol. 148, p. 342, 1909; Radium, p. 70, 1910. 



SLusby, Proc. Cambr., vol. 16, p. 26, 1911; Pbil. Mag., vol. 22, p. 775, 1911. 



••• II. A. Wilson, Phil. Mag., vol. 21, p. 711, 1911. 



* Blanc, Journal de physique, vol 7, p. 838, 1908. 



ti Wellisch, Radium, p. 241, 1909, and 1. c. 



« Lathey, Proc. Roy. Soc, vol. 84, p. 173, 1910. 



' Tyndall, Nature, vol. 84, p. .5.30, 1910. 



spranck. Verb. Deutsch. Phys. Gesellsch., vol. 12, p. 291, 1910. 



