NEW CHEMICAL REACTIONS. 79 



vapor of the nitrite was derived from a portion of its liquid 

 which had been accidentally introduced into the passage 

 through which the dry air flowed into the experimental tube. 



In this case, the electric beam traversed the tube for 

 several seconds before any action was visible. Decomposi- 

 tion then visibly commenced, and advanced slowly. When 

 the light was very strong, the cloud appeared of a milky 

 blue. When, on the contrary, the intensity was moderate, 

 the blue was pure and deep. In Briicke's important ex- 

 periments on the blue of the sky and the morning and 

 evening red, pure mastic is dissolved in alcohol, and then 

 dropped into water well stirred. When the proportion of 

 mastic to alcohol is correct, the resin is precipitated so 

 finely as to elude the highest microscopic power. By re- 

 flected light, such a medium appears bluish, by transmitted 

 light yellowish, which latter color, by augmenting the 

 quantity of the precipitate, can be caused to pass into 

 orange or red. 



But the development of color in the attenuated nitrite- 

 of-amyl vapor is doubtless more similar to what takes place 

 in our atmosphere. The blue, moreover, is far purer and 

 more sky-like than that obtained from Briicke's turbid 

 medium. Never, even in the skies of the Alps, have I 

 seen a richer or a purer blue than that attainable by a suit- 

 able disposition of the light falling upon the precipitated 

 vapor. 



Iodide of Allyl. Among the liquids hitherto subjected 

 to the concentrated electric light, iodide of allyl, in point 

 of rapidity and intensity of action, comes next to the 

 nitrite of arnyl. With the iodide I have employed both 

 oxygen and hydrogen, as well as air, as a vehicle, and found 

 the effect in all cases substantially the same. The cloud- 

 column here was exquisitely beautiful. It revolved round 

 the axis of the decomposing beam; it was nipped at certain 

 places like an hour-glass, and round the two bells of the 



flass delicate cloud-filaments twisted themselves in spirals, 

 t also folded itself into convolutions resembling those of 

 shells. In certain conditions of the atmosphere in the Alps 

 I have often observed clouds of a special pearly luster, 

 when hydrogen was made the vehicle of the iodide-of-ullyl 

 vapor a similar luster was most exquisitely shown. With 

 a suitable disposition of the light, the purple hue of iodine- 

 vapor came out very strongly in the tube. 



