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ir. The Combination of Hydrogen and Chlorine under the Influence of 
Light. 
By P. V. Beyan, M.A., Fellow of Trinity College, Cambridge. 
Communicated by Professor J. J. Thomsox, F.R.S. 
Received April 1,—Read May 14, 1903. 
Contexts. 
I. Historical introduction. 
II. Experimental investigation. 
1. The initial expansion. 
§ 1. The relation of the initial expansion to the time of insolation . 
§ 2. The relation to the hydrochloidc acid formed. 
§ 3. The temperature change associated with the initial expansion 
§ 4. Conclusions. 
§ 5. The expansion of chlorine alone under the influence of light . 
2. The final contraction. 
3. The period of induction. 
§ 1. Prolongation of the period of induction. 
The effect after darkening 
§ 3. The effect of impurities. 
§ 4. The effect of previous insolation of the separate gases 
§ .5. Expansion experiments. 
§ 6. Experiments with dried gases, and other experiments 
III. Theory of the action. 
Summary. 
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I. Historical Introdlctiox.''''^ 
In the year 1801, William CruickshankI noticed the gradual combination of a 
mixture of hydrogen and chlorine in diffuse daylight. Gay Lussac and Thexard 
observed that the mixture of these two gases exploded on exjiosure to direct sunlight. 
* For the historical introduction I am much indebted to a paper by Mellok in the ‘Journal of the 
Chemical Society,’ vol. 79, 1901. 
t Cruicxshank, ‘Nicholson’s Journal,’ 1801. 
I Gay Lussac and Thexard, ‘Mem. Soc. Phys. d’Arcueil,’ 1809. 
YOL. CCII.-A 347. 
21.10.03 
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