46 JVf. P faff on a deoxidating Property of [July, 



liquids were boiled in clean glass retorts, and great care was 

 taken to prevent any portion of them from being carried over 

 mechanically in the state of drops. The solutions on which the 

 action of the gases and vapours expelled by boiling was to be 

 determined, were contained in Woulfe's bottles, and, in general, 

 the vapours passed through two or three of these in succession. 

 The tubes of communication between the retort and the first 

 bottle, and between the bottles themselves, were plunged to a 

 sufficient depth in the solutions. 



1. The mere vapour of pure distilled water when passed through 

 a transparent solution of nitrate of silver, has the property of 

 communicating to it a discoloration, in proportion as it heats the 

 solution to the temperature of ebullition ; and the intensity of 

 this discoloration varies from yellow to dark-brown, according 

 to the concentration of the solution, and to the length of time 

 during which it has been exposed to the action of the vapour. 



2. This discoloration is inconsiderable, so long as the solution 

 of nitrate of silver remains under the boiling point, but it becomes 

 exceedingly striking;, the instant ebullition commences. The 

 colour which first appears is yellow, but it rapidly becomes 

 darker. The colour of the solution of nitrate of silver, when 

 sufficiently diluted, has a close resemblance to red wine. 



3. In the same manner, the solutions of nitrate of silver in the 

 remaining bottles may be discoloured; because the vapour, after 

 heating the liquid contained in one bottle, passes over into the 

 next, and raises its temperature also to the point of ebullition. 



4. This discoloration is caused by a deoxidation of the nitrate 

 of silver, and except that it. takes place with much greater rapi- 

 dity, it is similar in all respects to the effect produced by light. 

 In proof of this we may mention, a. The similarity of the colours 

 with those produced by the action of mere light, b. The com- 

 plete removal of the colour, and restoration of transparency, by 

 the addition of nitric acid. c. The similar deoxidizing effect of 

 the vapour of water upon other metallic solutions, which are 

 easily deoxidized, either by light, or by some chemical action. 

 d. The disengagement of oxygen gas during the process. 



5. The most convincing of all proofs is furnished by a solution 

 of muriate of gold. A solution of this salt so much diluted as 

 scarcely to retain a shade of yellow, when heated to the boiling 

 point by a stream of the vapour of water, acquires a beautiful 

 blue colour, exactly similar to the colour produced in it by tinc- 

 ture of nutgalls, oxalic acid, &c. 



6. After the expulsion of the atmospheric air, I collected the 

 gas which was disengaged in a constant stream of minute 

 bubbles, from the boiling-hot solution of nitrate of silver. It 

 proved to contain a considerably greater quantity of oxygen than 

 common air: 100 volumes of it mixed with 100 volumes of 

 nitrous gas, sustained a diminution amounting to 91, whereas 

 common air sustained a diminution of only 80. 



