To ascertain whether any change in the constitution of the nitrous oxide had been produced by the condensation, I introduced a small quantity of sulphite of potash, with excess of alkali, that had absorbed nitrous oxide, into a long and thin cylindrical tube filled with mercury; and inclining it at an angle of 35° with the plane of the mercury, applied the heat of a spirit lamp to that part of the tube containing the salts; when the glass became very hot, gas was given out with rapidity; in less than a minute the tube was full. This gas was transfered into another tube, and examined; it proved to be nitrous oxide in its highest state of purity;[157] for a portion of it absorbed by common water, left no more than a residuum of ¹/₁₅, and sulphur burnt in it with a vivid rose-colored flame. [157] Hence we learn that sulphite of potash, when strongly heated, does not decompose nitrous oxide, even in the _nascent state_. Being now satisfied that the alkalies were capable of combining with nitrous oxide; to investigate with precision the nature of these new compounds, I proceeded in the following manner. VII. _Combination of Nitrous Oxide with Potash._ _a._ Into a solution of sulphite of potash, which had been made by passing sulphureous acid gas from a mercurial airholder into caustic potash dissolved in water, I introduced 17 grains of dry potash. The whole evaporated at a low temperature, gave 143 grains of salt. This salt was not _wholly_ composed of sulphite of potash and potash; it contained as well, a minute quantity of carbonate, and sulphate of potash, formed during the evaporation.[158] [158] See the excellent memoir of Fourcroy and Vauquelin on the sulphureous acid, and its combinations. Annales de Chimie, ii, 54. Or Nicholson’s Phil. Journal, vol. i, pag. 313. 120 grains of it finely pulverised, and retaining the water of crystalisation, were exposed to 15 cubic inches of nitrous gas, over mercury. The nitrous gas diminished with great rapidity, and in three hours a cubic inch and nine tenths only remained, which consisted of nearly one third nitrous oxide, and two thirds nitrogene that had pre-existed in the nitrous gas. The increase of weight of the salt could not be determined, as some of it was lost by adhering to the vessel in which the combination was effected, and to the mercury. It presented no distinct series of crystalisations, even when examined by the magnifier; rendered green vegetable blues, and its taste was very different from that of the remaining quantity of salt that had been exposed to the atmosphere. A portion of it strongly heated over mercury, gave out gas with great rapidity, which had all the properties of the purest nitrous oxide. When water was poured upon some of it, no gas was given out, and the whole was equably and gradually dissolved. Alcohol, as well as ether, appeared incapable of dissolving any part of it.