94 



Prof. Tyndall on a New Series of 



[Recess, 



When dry oxygen was employed to carry in the vapour, the effect was 

 the same as that obtained with air. 



When dry hydrogen was used as a vehicle, the effect was also the 

 same. 



The effect, therefore, is not due to any interaction between the vapour of 

 the nitrite and its vehicle. 



This was further demonstrated by the deportment of the vapour itself. 

 When it was permitted to enter the experimental tube unmixed with air or 

 any other gas, the effect was substantially the same. Hence the seat of the 

 observed action is the vapour itself. 



With reference to the air and the glass of the experimental tube, the 

 beam employed in these experiments was perfectly cold. It had been sifted 

 by passing it through a solution of alum, and through the thick double- 

 convex lens of the lamp. When the unsifted beam of the lamp was em- 

 ployed, the effect was still the same ; the obscure calorific rays did not ap- 

 pear to interfere with the result. 



I have taken no means to determine strictly the character of the action 

 here described, my object being simply to point out to chemists a method 

 of experiment which reveals a new and beautiful series of reactions ; to 

 them I leave the examination of the products of decomposition. The mo- 

 lecule of the nitrite of amyl is shaken asunder by certain specific waves of 

 the electric beam, forming nitric oxide and other products, of which the 

 nitrate of amyl is probably one. The brown fumes of nitrous acid were 

 seen to mingle with the cloud within the experimental tube. 



The nitrate of amyl, being less volatile than the nitrite, could not main- 

 tain itself in the condition of vapour, but would be precipitated in liquid 

 spherules along the track of the beam. 



In the anterior portions of the tube a sifting action of the vapour occurs, 

 which diminishes the chemical action in the posterior portions. In some 

 experiments the precipitated cloud only extended halfway down the tube. 

 When, under these circumstances, the lamp was shifted so as to send the 

 beam through the other end of the tube, precipitation occurred there also. 



Action of Sunlight. 

 The solar light also effects the decomposition of the nitrite- of- amyl vapour. 

 On the 10th of October I partially darkened a small room in the Royal 

 Institution, into which the sun shone, permitting the light to enter through 

 an open portion of the window-shutter. In the track of the beam was 

 placed a large plano-convex lens, which formed a fine convergent cone in 

 the dust of the room behind it. The experimental tube was filled in the 

 laboratory, covered with a black cloth, and carried into the partially darkened 

 room. On thrusting one end of the tube into the cone of rays behind the 

 lens, precipitation within the cone was copious and immediate. The vapour 

 at the distant end of the tube was in part shielded by that in front, and 



