1824.] Deoxidating Property oj f'the Vapour of Water. 45 



the action of the air, which do not take place till after several 

 hours in the bulk of the solution. It follows, therefore, that 

 when we re-immerse the lamina, we bring in contact two dissi- 

 milar liquids, and nothing in that case opposes the production 

 of an electrical current. 



" On the other hand, since the immersion of platina lamina? 

 in a solution of nitrate of zinc does not produce any current, 

 although it contains deutoxide of azote and nitrous gas, it is 

 probable that this may be owing to the nitrate not suffering any 

 change by contact with the air, in consequence of the metal 

 being capable of forming only one oxide." 



Article IX. 



On a deoxidating Property oj the Vapour of Water. 

 By C. H. Pfaff* 



It was remarked by Hermbstadt, while making the experi- 

 ments from which he deduced the existence of a peculiar colour- 

 ing principle in sea-water, and its superincumbent atmosphere, f 

 that if that liquid be boiled in a retort, and if, by means of a glass 

 tube attached to the beak of the retort, the gases and aqueous 

 vapour evolved be made to pass through a solution of nitrate of 

 silver, the latter by degrees assumes the colour of red wine, and 

 at the end of 24 hours, a broxvnisli-yellow coloured sediment is 

 deposited. I observed the same appearance, on repeating this 

 experiment with sea-water from the bay at Kiel. As, however, 

 I had reasons for suspecting that this change is not occasioned 

 by any peculiar gaseous constituent, I prepared an artificial 

 mixture of solutions of the muriates of magnesia and soda, in the 

 proportions which constitute sea-water, and on making the ex- 

 periment with this, I still obtained the same result. I observed 

 •also that the colour imparted to the solution of nitrate of silver 

 at the beginning, and towards the conclusion ofthe experiment, 

 is different: at first it is a weak, violet, but after the experiment 

 has gone on for some time (provided there be a sufficient quan- 

 tity ofthe metallic salt in the vessel through which the vapours 

 pass), it has a considerable infusion of reddish-brown. Hence 

 I considered it not unlikely, that in these experiments there are 

 two distinct causes which produce discoloration. This induced 

 me to repeat the experiment in a variety of ways ; which at. last 

 conducted me to the following very interesting results. 



Tin; experiments themselves are extremely simple. 'flu' 



* Schweigger's Journal t'lir Chemie uml I'hysik, xxxvi. (>S. 

 i Thit opinion was refuted by Pfaff in a smalt pamphlet, entitled T)ai Kicltr "Set- 

 bad i' rglichcn mitandern Beeb'ddern an </<;■ Ottne and Nor date, Kiel) lt>'iV. 



