A MP

AMM ( 55 )

being attributed to the ammonia absorbed by themoistened potash.

Sir H. Davy has also made a number of expe-riments on this singular compound with resultssome of which agree with those of Messrs. GayLussac and Thenard, and others differ fromthem. Some of these we shall mention, 11 par-ticularly the properties of the residuum of theolive-green substance after it has been heated toredness.

Its colour is black and in lustre it resemblesplumbago. It is opake, and brittle. It is aconductor of electricity. It does not fuse at alow red heat, but gives out a dark colouredsublimate. When exposed to the air at a com-mon temperature it usually takes lire imme-diately and burns with a deep red light. Whenit is acted upon by water it heats, effervescesviolently, and is resolved into ammonia andpotash, with a little inflammable gas. It has noaction upon quicksi'ver. It combines withsulphur and phosphorus by heat, and thesecompounds when wetted inflame and give out,the one sulphuretted, and the other phosphu-retted hydrogen gas.

On distilling this substance in a tube ofwrought platina in a very intense heat, potashwas found with a quantity of potassium in thetube, and the gas was hydrogen with only asmall proportion of azote.

The remarkable circumstance of this experi-ment is the deficiency of azote, this substancebeing in much less proportion than is requiredto constitute ammonia if the analysis of thisalkali by electricity be at all correct.

After all that has been done on the analysisof ammonia, no satisfactory proof has yet beengiven that it can be decomposed into any otherelements than azote and hydrogen.AMMONIAC. (Gum.)

This gum has been examined by M. Bracon-notff Exposed to a very gentle heat it loses 6per cent, of its weight of mere moisture. .Dis-tilled per se, it yields half its weight of a brownempyreumatic oil containing ammonia. Thecoal contains phosphat and carbonatof lime.

Twenty five grammes of gum ammoniac wereboiled with alcohol. The whole was dissolvedexcept 5.8 grammes,, and the solution remainedclear on cooling. The insoluble portion washeated with water and the greater part dissolved,leaving however a grey glutinous mass insolubleboth in water and spirit of wine.

The watery solution left a gum on evapora-tion, which was transparent, reddish yellow,

> k Phil. Trans, for 1809..

slightly bitter, and brittle: water easily dissolvesit. It is abundantly precipitated by Goulard’sextract, (but not by the acetite of lead) and onlyvery partially by the nitrats of mercury and oflead. Lime water does not alterthe solution, butoxalat of ammonia separates some oxalat of lime.

The resin produced by the evaporation ofthe alcoholic solution of gum ammonia is red-dish yellow, transparent, brittle, but easilysoftens between the fingers. It has no taste.It unites with the alkalies with ease, even with-out heating, and the result is a saponaceousbitter solution.

Sulphuric acid dissolves the resin quietly inthe cold, and the solution is separated by water.-

When nitric acid is heated on this resin, it issuddenly decomposed with much red vapour.On evaporating the liquor to dryness a bitterresin is obtained which melts at a low heat,unites to alkalies, dissolves in alcohol and inwater, and precipitates in part from the latter ifit has been used boiling. Cold water also dis-solves much of this bitter resin, giving a verybeautiful yellow colour that stains the fingersstrongly, and fixes itseif easily and most firmlyto silk and wool, so as to become unalterable byoxymuriatic acid, and even by alkalies if weak.

Gum ammoniac contains 18.4 per pent, ofgum; 70. of resin ; 4.4 of matter resemblinggluten ; and (i of moisture.

AMPHIBOLE.

At the end of the article of Str AHT.STErN it is-remarked that a strong analogy subsists betweenthe several varieties of Hornblende , Actynolite,Tremolite, and Asbestus. M. Hauy has since,in his Tableau comparatif, entered into an in-teresting discussion of this question, and fromcrystallographical resemblances, aided by theresults of recent chemical analysis, has arrangedthem in the following manner.

The Labrador Hornblende forms a species byitself r under the name HyperstenE. The re-splendent Hornblende (Schiilerspath or Bron-zite) forms a variety of Diallagf., the metal-loide. A few of the Strahlsteins constitute thespecies Epidote, (Thallite ofKarsten) the re-mainder of tl:e Hornblendes and Strahlstein, andall the Tremolites are included under the speciesAmphibole. Asbestus for the present ranks asa distinct species, but M. Hauy cites with evi-dent favour the opinion of Cordier, who is forincluding it under Amphibole. ,

The following are the essential crystallogra—phical characters of amphibole. Its primitivecrystalline form is an oblique rhomboidal prism,

a An. Chem. tom. 68.