“Accordingly I procured some volatile spirit of sal ammoniac, and having put it into a thin phial, and heated it with the flame of a candle, I presently found that a great quantity of vapour was discharged from it; and being received in a vessel of quicksilver, standing in a basin of quicksilver, it continued in the form of a transparent and permanent air, not at all condensed by cold; so that I had the same opportunity of making experiments upon it as I had before on the acid air, being in the same favourable circumstances.... Wanting, however, to procure this air in greater quantities, and this method being rather expensive, it occurred to me that alkaline air might probably be procured, with the most ease and convenience, from the original materials, mixed in the same proportions that chemists had found by experience to answer the best for the production of the volatile spirit of sal ammoniac. Accordingly I mixed one-fourth of pounded sal ammoniac with three-fourths of slaked lime; and filling a phial with the mixture, I presently found it completely answered my purpose. The heat of a candle expelled from this mixture a prodigious quantity of alkaline air; and the same materials ... would serve me a considerable time without changing....” He next studied the properties of the alkaline air. He found, of course, it was readily soluble in water. “Having satisfied myself with respect to the relation that alkaline air bears to water, I was impatient to find what would be the consequence of mixing this new air with the other kinds with which I was acquainted before, and especially with _acid_ air; having a notion that these two airs, being of opposite natures, might compose a _neutral air_, and perhaps the very same thing with common air. But the moment that these two kinds of air came into contact a beautiful white cloud was formed, and presently filled the whole vessel in which they were contained.... When the cloud was subsided there appeared to be formed a solid _white salt_, which was found to be the common _sal ammoniac_, or the marine acid united to the volatile alkali.... “_Fixed air_ admitted to alkaline air formed oblong and slender crystals.... These crystals must be the same thing with the volatile alkalis which chemists get in a solid form by the distillation of sal ammoniac with fixed alkaline salts.... “Alkaline air, I was surprised to find, is slightly inflammable.... “That alkaline air is lighter than acid air is evident from the appearances that attend the mixture, which are indeed very beautiful. When acid air is introduced into a vessel containing alkaline air, the white cloud which they form appears at the bottom only and ascends gradually. But when the alkaline air is put to the acid the whole becomes immediately cloudy quite to the top of the vessel.”