84 M. Adolph Rose on the Combination of Hydrate d 



oxide of manganese, whicli, on the presence of nitric acid is 

 not, but on that of nitric oxide and nitrous acid is, immediately 

 decolorated ; however, the solution of the hypermanganate of 

 potash is far more sensitive. 



A portion of the residuum from the distillation of the sul- 

 phuric acid with nitric acid, was distilled in a small retort 

 over an alcohol lamp, with the precaution that the passing 

 product of distillation was frequently removed and tested. At 

 first a sulphuric acid passed over, which contained very little 

 nitric oxide ;. however, the amount of this latter increased in 

 the succeeding portions more and more ; and the last was a 

 concentrated solution of the sulphate of nitric oxide in sul- 

 phuric acid, which acted towards reagents exactly like the 

 solution of the sulphate of nitric oxide in sulphuric acid pre- 

 sently to be mentioned. Only a trace of the sulphate of lead 

 remained in the retort. The last product was white, became 

 yellow on heating, and on diluting it with water, green, blue, 

 and lastly, colourless, under the evolution of much nitric 

 oxide. 



I hereupon attempted to prepare direct a combination of 

 nitric oxide with hydrated sulphuric acid. I passed nitric 

 oxide dried over the chloride of calcium, into distilled English 

 sulphuric acid which was placed in a large vessel, but so that 

 the entrance of air was prevented. A rapid absorption took 

 place when the disengagement was not effected too violently, 

 and no gas could be observed to escape; only when the evolu- 

 tion was too violent did nitric oxide escape. At the same time, 

 a crystalline crust was formed on the sides of the vessel, which, 

 however, disappeared again when the glass was shaken, it be- 

 ing dissolved by the acid. After passing the nitric oxide 

 through for some time the liquid became lilac, then slightly 

 blue, and at last, beautiful dark blue, without any increase of 

 temperature being perceptible. The liquid became thicker 

 and thicker, and on shaking the vessel ran down its sides like 

 a thick syrup; on shaking it was converted into a white frothy 

 mass, which, however, on being left to stand, again changed 

 into the blue syrup. By continually passing nitric oxide 

 through it, it was at last converted into a solid white cry- 

 stalline mass, which melted on being slightly heated without 

 decomposition, and on cooling, again solidified. 



If I passed nitric oxide not dried over the chloride of cal- 

 cium, into English sulphuric acid, a slight increase of tempera- 

 ture occurred ; nevertheless, the crystals then appeared to form 

 more rapidly, so that it seems that a little aqueous vapoux* 

 favours their formation. 



