492 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 

 I. Chemistry and Physics. 



1. On the Action of Light on Chlorine water. — It is frequently 

 assumed that when an aqueous solution of chlorine is exposed to- 

 light, the whole of the chlorine unites with the hydrogen of the 

 water setting free an equivalent quantity of oxygen. Pedler 

 has investigated this reaction, using the sunlight of Calcutta to 

 effect it. He finds that chlorine and water have comparatively 

 little action on each other, even in tropical sunlight, when the 

 number of water molecules is not more than one hundred times 

 the number of chlorine molecules. When the number of water 

 molecules is 150 times that of the chlorine molecules, the action 

 may reach 50 per cent of that actually possible. And even when 

 it reaches 400 times, the reaction, while more rapid, reaches only 

 four-fifths of the possible amount. In ordinary chlorine water, 

 saturated at 30°, there is about - 5566 grams of chlorine in 100 

 c. c. of water; or about 708 molecules of water to each molecule 

 of chlorine. So that with such a solution, the decomposition mav 

 be expected to be both more rapid and more complete. Experi- 

 ments with this solution show that in full sunlight the main 

 reaction which takes place is that represented by the equation 

 (H a O) a + (Cl 2 ) s =(HC]) 4 + O a ; while in feeble diffused light, the 

 reaction at first is probably H„0 + C1 2 =HC1 + HC10 ; this hypo- 

 chlorous acid being in its turn decomposed by light and yielding 

 chloric acid. So that the final reaction is (C1 2 ) 4 + (H 2 0) 4 = 

 (HCl)„ + HC10 s + 0. Hence the action of chlorine on water is, in 

 its first stages at least, quite similar to that of chlorine on cold 

 dilute solutions of potassium or sodium hydrate. In its second 

 stage, the action of chlorine on water is similar to its action on 

 hot concentrated solutions of these hydrates. — J. Chem. Soc> 

 lvii, 613, July, 1890. G. e. g. 



2. On the Action of Light on Phosphorus. — Pedler has ex- 

 tended to phosphorus his investigations upon the action of light 

 upon chemical substances. A glass tube was filled with a nearly 

 saturated solution of phosphorus in carbon disulphide, sealed and 

 exposed to full sunlight. In a few minutes a yellowish red coat- 

 ing began to form on the sides of the tube, and continued until 

 the interior was covered. After about three weeks' daily ex- 

 posure to sunlight, the tube was opened and the precipitate 

 examined. After washing with carbon disulphide, a bright red 

 powder was obtained, which under the microscope appeared to be 

 a mixture in about equal parts, of bright sulphur-yellow particles 

 and bright red particles. The powder remained unchanged in 

 the air, and was unacted on by water, alcohol, ether, benzene and 

 carbon tetrachloride. A warm dilute solution of sodium hydrate,, 

 however, dissolved it readily with evolution of gaseous hydrogen 

 phosphide. On cautious heating, the yellow portion sublimed, 

 leaving the red portion. The sublimate was partially soluble in 



