VOL. LXXIX.], PHILOSOPHICAL TRANSACTIONS. (JO^ 



ductions are much the same, and the only new circumstance is, as was observed 

 at art. 5. The same effects are brought about instantly by the action of red-hot 

 iron, which require much time by the method of simple exposure to cold iron. 

 For which reason, though it gave him much pleasure at the time to see such 

 curious transmutations brought about in a few minutes, yet it scarcely appeared 

 worth while to trouble the r. s. with a detail of the experiments ; and he only 

 does it now, because the conjectures he then formed have been sufficiently veri- 

 fied by future experiments. The conjectures were as follow: 



10. Almost immediately on seeing the volatile alkali produced by means of 

 nitrous acid and metals, Mr. M. conceived the possibility of inverting the order 

 of the process, and of producing nitrous acid or nitrous air by the decomposition 

 of volatile alkali. He knew of no experiments where this had been done, or any 

 thing like it; yet as volatile alkali was beyond all dispute produced in the method 

 just described, and as the iron turnings and inside of the gun-barrel were left 

 after the operation in a state of calcination, it seemed not unnatural to suppose, 

 that by forcing volatile alkali through the red-hot calces of some of the metals, 

 nitrous acid or nitrous air might be produced; though in fact he neglected for 

 near 1 years actually to make the trial. It was some time in the month of 

 March, 1788, that the calx of manganese on account of its very great infusi- 

 bility, and its yielding abundance of dephlogisticated air, occurred as a very pro- 

 per substance for the purpose. He immediately crammed a gun-barrel full of 

 powdered manganese; and to one end of the tube he applied a small retort, con- 

 taining the caustic volatile alkali. As soon as the manganese was heated red-hot, 

 a lighted candle was placed under the retort, and the vapour of the boiling vola- 

 tile alkali forced through the gun-barrel. Symptoms of nitrous fumes and of 

 nitrous air soon discovered themselves, and by a little perseverance he was enabled 

 to collect considerable quantities of air, which on trial proved highly nitrous. 

 He afterwards frequently repeated this experiment, and always in some degree 

 succeeded. Much depends on the kind of manganese employed, much on the 

 heat of the furnace, and much on the patience of the operator; as these are va- 

 ried, there will be great variations of the products. 



1 1 . In general Mr. M. made use of clean gun-barrels with which no previous 

 experiments had been made. The manganese was used in rough powder; for 

 when'it is too finely powdered, the tube is choked, and the air cannot pass. In 

 some experiments he applied the vapour of the volatile alkali directly to the hot 

 manganese. In others he suffered the manganese to remain a considerable time 

 in a red heat before he made the volatile alkali, contained in the retort at the end 

 of the tube, to boil; and by this means informed himself of the nature of the airs 

 which the manganese yielded per se. In neither case could he ever perceive the 

 least appearance of nitrous acid or nitrous air till the volatile alkali was used. 



VOL, XVI. 4 I 



