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ELEMENTS OF MATERIA MEDICA.

It appears from the observations of Davy and Dalton that the specificgravity of mixtures of liquid ammonia and water is exactly the mean ofthat of the two ingredients.

Composition. —From the above observations the composition of offici-nal solutions of ammonia is nearly as follows:—

Lond. Ph. Dub. Ph. U. S. Ph. Ed. Ph. Liq. am. fort.

(sp.gr. 0-960) (sp. gr. 0’950) (sp. gr. 0'944) (sp. gr. 0-939) (sp.gr.0’880)

Ammoniacal gas . 10. 12'5. 14'5. 15'8.30'5

Water. 90 87'5. 85'5.84'2. 69’5

Liquor Ammonise 100.lOO'O.lOO'O.lOO'O.lOO'O

Characteristics.— (See Ammoniacal Gas).

Impurities. —Liquor ammonia; frequently contains traces of the car-bonate of ammonia which may be detected by lime-water, or by a solu-tion of the chloride of calcium, either of which occasions a white preci-pitate of the carbonate of lime. When a portion of the liquid has beenneutralized by pure nitric acid, it ought not to cause a precipitate by theaddition of the nitrate of silver, of oxalic acid, or of sesquicarbonate ofammonia : for the first would indicate the presence of hydrochloric acid,or chlorine ; the second, of lime ; the third of lime, or other earthy matter.

Incompatibles. —It is hardly ‘necessary to say that all acids areincompatible with ammonia. With the exception of the salts ofpotash, soda, lithia, lime, baryta, and strontia, ammonia decomposesmost of the metallic salts.

Physiological Effects.— {a.) On vegetables. —The effects of ammo-nia on plants have been before noticed.

( b.) On animals .—Orfila injected sixty grains of liquor ammonias intothe jugular vein of a strong dog: tetanic stiffness immediately came on,the urine passed involuntarily, and the animal became agitated byconvulsions: death took place in ten minutes. The body was imme-diately opened, when the contractile power of the muscles was foundextinct. In another experiment, thirty-six grains of concentrated solu-tion of ammonia were introduced into the stomach, and the oesophagustied: in five minutes the animal appeared insensible, but in a few mo-ments after was able to walk when placed on his feet; the inspirationswere deep, and his posterior extremities trembled. In twenty hours hewas insensible, and in twenty-three hours died. On dissection themucous membrane of the stomach was found red in some places. Theseexperiments show the effects of large doses of this solution on the ner-vous system. The first experiment agrees in its results (that is, incausing tetanic convulsions) with that made by Nysten, and which hasbeen before mentioned, of throwing ammoniacal gas into the cavity of thepleura. From the convulsions it may be inferred that in these instancesthe (grey matter of the) spinal marrow was specifically affected.

(c.) On man. a. Local effects .—In the concentrated form the localaction of liquor ammonias is exceedingly energetic. Applied to the skinit causes pain, redness, vesication, and destruction of the part; thusacting first as a rubefacient, then as a vesicant, and lastly as a caustic orcorrosive. Its emanations are also irritant: when they come in contactwith the conjunctival membrane, a flow of tears is the result; wheninhaled, their powerful action on the air-passages is well known. Per-sons in syncope are observed to be almost immediately raised from a