8 Prof. Schoenbein on the Discovery of Gun-Cotton. 



called hydrated sulphuric acid, and that SO^ placed in pre- 

 sence of BaOg or PbO^ gives rise to what is called sulphate 

 of the oxide of barium or of lead. Rose's compound, to which 

 the formula 2SO3 + NO2 has been assigned, should have, in 

 my opinion, 2863+ NO4. Admitting this, I considered it 

 probable that the mixture of 2(S02+H02) ( = 2(803+00)) 

 with NO4+HO2 ( = N05+H0) yields 28O2+NO4, and 

 that at the same time SHOg is disengaged, or enters into 

 a loose combination with what is called the bisulphate of 

 deutoxide of nitrogen. In other words, I conjectured that a 

 mixture formed with the hydrates of nitric acid and sulphuric 

 acid would possess a very great power of oxidation, and would 

 form a kind of aqua regia, in which the combination HOg 

 would act the part of the chlorine. On this hypothesis, and 

 abstracting HO2 from the acid mixture by means of a proper 

 oxidable body, there ought to remain Rose's compound. 



Guided by these suppositions, which, I admit, may be as 

 little founded as they are contrary to the ideas received among 

 chemists, I commenced in December 184-5 a series of experi- 

 ments with a view to put my hypothesis to the proof: it will 

 be seen in the sequel whether the results at which I arrived 

 tend to confirm it. 



I mixed some flowers of sulphur and a certain quantity 

 of the acid mixture of which I have spoken : immediately, 

 even at the temperature of 32° F., a lively disengagement of 

 sulphurous acid gas took place without the production of 

 deutoxide of nitrogen. After the reaction, which was accom- 

 panied by a development of heat, there remained a colourless 

 liquid, which, mixed with water, disengaged a considerable 

 quantity of deutoxide of nitrogen, and acted generally as a 

 solution of Rose's compound in hydrated sulphuric acid would 

 have done. 



I should add here, that a mixture of four ounces of hydrated 

 sulphuric acid with a single drop of nitric acid, on the addition 

 of flowers of sulphur, disengages a sensible quantity of sulphu- 

 rous acid. To assure himself of the presence of the latter, the 

 operator has only to hold over the liquid a strip of paper which 

 has been covered with iodide of potassium paste, and tinged 

 slightly blue by exposure to chlorine. The liberated sulphu- 

 rous acid will soon dissipate this blue colour. 



Selenium and phosphorus are oxidized in the same manner 

 at low temperatures in the acid mixture in question ; and this 

 latter is modified to such an extent, that, on the addition of 

 water, an abundant disengagement of deutoxide of nitrogen gas 

 takes place. 



Iodine even, in the state of powder and shaken up with the 



