In order, if possible, to procure the amalgams in quantities sufficient for distillation, he combined the methods he had employed in the first instance, with those pursued by Berzelius and Pontin. "A mixture of the earth with red oxide of mercury was placed on a plate of platina, a cavity was made in the upper part of it to receive a globule of mercury, the whole was covered by a film of naphtha, and the plate was made positive, and the mercury negative, by a proper communication with the battery of five hundred." The amalgams thus procured were afterwards distilled in glass tubes filled with the vapour of naphtha; by which operation the mercury rose pure from the amalgam, and it was very easy to separate a part of it; but the difficulty was to obtain a complete decomposition, for to effect this, a high temperature was required, and at a red heat the bases of the earths instantly acted upon the glass, and became oxidated. In the best result which Davy obtained in this manner, the barytic basis appeared as a white metal of the colour of silver, fixed at all common temperatures, but fluid at a heat below redness, and volatile at a heat above it. Unlike the alkaline bases, it would seem to be considerably heavier than water. In extending these experiments to alumine, silex, zircone, &c. after a most elaborate investigation, such results were not obtained as justified the conclusion that they were, like the other earths, metallic oxides; although, as far as they went, they added to the probability of such analogy. It will be remembered that, after the fixed alkalies had been found to contain oxygen, Davy was very naturally led to enquire whether ammonia might not also contain the same element, or be an oxide with a binary base. In the communication from Professor Berzelius, and Dr. Pontin, already alluded to, a most curious experiment is related on what they consider the deoxidation and amalgamation of the compound basis of ammonia; and which they regard as supporting the idea which Davy had formed of the presence of oxygen[83] in the volatile alkali. A fact so startling as the production of a metallic body from ammonia, or from its elements, immediately excited in Davy's mind the most ardent desire to pursue the enquiry; and, after repeating the original experiments of the Swedish chemists with his accustomed sagacity, he modified his methods of manipulation, in order, if possible, to obtain this metallic body in its most simple form; but, although he succeeded in producing the amalgam without Voltaic aid, by the intervention of potassium, he could not so distill off the mercury as to leave the basis, or imaginary _ammonium_, free. [83] See page 285.