A M M

( 52 ) A M M

which are about 28 measures of azote gas to 72 Mr. Dalton adds the following estimation,measures of hydrogen in the hundred.

ICO measures of ammonia at .6 sp. gr, weigh 60 grains.

These become by decomposition J85. measures of mixed gas,

Namely 51.8 of azote which at .967 sp.gr. weigh 50.09133.2 of hydrogen .08 10.65

60.71

Here the united weights of the hydrogenand azote equal and a little exceed the weightof the ammonia, and hence this alkali cannotcontain any other constituent part than azoteand hydrogen.

Mr. Dalton remarks on the analysis of ammo-nia by mixture with oxygen and detonation, thatnotwithstanding the elegance and expedition ofDr. Henry’s method, it appears probable that acompound combustible such as ammonia is, cannever be totally decomposed and one of its ele-ments burnt, to the entire exclusion of the other.Thus in a mixture of carbonic oxyd and hydro-gen, phosphorus, &c. where one of the elementsseizes oxygen with more rapidity than the other,it is impracticable totally to oxygenate one ofthem, and leave the other untouched. Withammonia it is confessedly so where an excess ofoxygen is used, (nitric acid appearing along withthe water produced; and Mr. Dalton conceivesthat this is in some degree the case in whateverproportions they are fired. On the whole heprefers employing nitrous oxyd. When 100.measures of ammonia are exploded with 120. ofnitrous oxyd, the gasses resulting are azotewith only a very small portion of hydrogen. Ifto this a little hydrogen be added, and then anexcess of oxygen, another explosion will deter-mine the residuary hydrogen before explosion,which being deducted, there remain about 172measures of azote, 120 of which come from thenitrous oxyd, and 52 from the ammonia, whichgives after the rate of 28 per cent, of azote involume on the evolved gasses.

We now proceed to the very interesting re-searches of Sir H. Davy on the nature of am-monia.

This eminent philosopher, after his most im-portant discovery of the metallic bases of thefixed alkalies, was led from analogy to entertainthe opinion that ammonia was probably, like theother alkalies, a compound of some peculiarmetallic base and oxygen, and some experimentson the decomposition of ammonia, gave himreason to suppose that the hydrogen and azoteevolved, were less than the entire weight of the

alkali by about to which eleventh part heconcluded was the oxygen of the ammonia.This opinion, however, has been satisfactorilyrefuted by the laborious researches of Henryand Berthollet , just described; so that whenammonia is decomposed simply into hydrogenand azote, it appears that the united weights ofthese two elements equal the weight of the am-monia decomposed with as much accuracy ascan be ever expected from such delicate expe-riments. This part of the controversy thereforeseems to be put at rest, but another and highlycurious set of phenomena happened to be dis-covered at the same time, which deserves par-ticular notice.

Dr. Seebeck, of Jena, discovered in 1808, thatwhen solid carbonat of ammonia is slightlymoistened and placed in contact with mercury,and the whole connected with the Voltaic bat-tery so that the mercury communicates with thenegative pole and the salt with the positive pole,the mercury speedily becomes as soft as butter,expands in bulk, and has all the appearance of aitamalgam. This when thrown into water efFer-vesces strongly, the water becomes ammoniacaland the mercury returns to its original state. Thisexperiment was repeated by Dr. Pontin andProfessor Berzelius with some variation, and bythem communicated to Sir H. Davy , e who imme-diately pursued the subject with his accustomedskill and ingenuity. His principal experimentsare the following : a cavity was made in a pieceof muriat of ammonia, and into this a large glo-bule of mercury was introduced. The muriatwas slightly moistened and placed on a plate ofplatina, which was made positive in the circuitof the large battery. The quicksilver was madenegative by means of a platina wire. A strongeffervescence immediatelytook place, the globulein a few minutes enlarged to five times its for-mer dimensions, and metallic crystallizationsshot from it as a centre round the body of the salt,which, when accidentally broken off from themass, rapidly disappeared, emitting ammoniacalfumes and reproducing mercury.

When a piece of moistened carbonat of am--

Phil. Trans, for 1808 and 1809.