174

ELEMENTS OF MATERIA MEDICA.

half of powdered chalk, and sublime with a gradually increased heat.In this process three equivalents or 162 parts of hydroclilorate of am-monia react on three equivalents or 150 parts of carbonate of lime, andproduce two equivalents or 118 parts of the hydrated sesquicarbonateof ammonia, three equivalents or 168 parts of chloride of calcium, oneequivalent or 17 parts of ammonia, and one equivalent or 9 parts ofwater. The chloride of calcium is left in the subliming pot, thehydrated sesquicarbonate is sublimed, while the ammonia and waterare dissipated.

INGREDIENTS USED.

RESULTS.

C3en ATur Am 111 5 3 ^1* Hydr. 33 eq. Mur \ 3eq.Mur.A».lll ^ 3eq Chlor# 108

Amm. 162") 1 eq. Ammonia. 17

o Pn ca.rb f 3 eq. Carb . Acid. 66 -

Lime) 150^3 eq. Lime, 84 --^ 3 ^ Calc^'. ^

2eq.Water, 18^

1 eq. Water .

[••I

1 eq. Amm.17 \ .=2

2 eq. Hyd. Sesquic. Amm. 1183eq.ChlorideCalcium .. 168

Sesquicarbonate of ammonia is generally procured on the large scaleby subliming the ingredients in an iron pot, to which an earthen orleaden head is adapted as a receiver. As a substitute for hydroclilorateof ammonia, manufacturers frequently employ impure sulphate of am-monia; but the resulting sesquicarbonate is sometimes contaminatedwith a little tar or oil, and deposits a dark carbonaceous matter whendissolved in acids.

Properties.— Sesquicarbonate of ammonia is met with in the formof fibrous, white, translucent cakes, about two inches thick. When ex-posed to the air it evolves carbonate of ammonia, and is converted intobicarbonate of ammonia; so that its vapour has a pungent odour, andstrongly reddens turmeric paper. The resulting hydrated bicarbonate isopaque, pulverent, and much less pungent, from which it has beentermed mild carbonate of ammonia. The sesquicarbonate is soluble infour times its weight of cold water; hut boiling water or alcohol decom-poses it, dissolving the carbonate of ammonia, and evolving carbonic acid.

The liquor ammonia sesquicarbonatis (Ph. L.) is prepared by dis-solving four ounces of this salt in a pint of water.

Characteristics. —This is recognized as an ammoniacal salt by itsodour, its fugacious action on turmeric paper, and by the action of itssolution on the salts of copper and on the chloride of platinum (seeAmmonia). From a solution of caustic ammonia it may be distinguishedby the white precipitate which it produces with the calcareous salts.From the monocarbonate this salt is distinguished by the effervescencecaused when it is put into boiling water or alcohol. From the bicar-bonate it may be known by its greater pungency and solubility.

Composition. —This salt consists, according to Mr. Phillips ( QuarterlyJournal of Science, vol. vii. p. 294) and Dr. Thomson, of carbonic acid,ammonia, and water, in the following proportions:—

Eq. Eq. Wt. Per eentage. R. Phillips.

Carbonic Acid. 3 66 55'93 . 54-2

Ammonia. 2 34 28-81 29\3

Water .2. 18. 15-26. 16-5

Hydrated Sesquicarbonate of Ammonia 2.118.lOO'OO.lOO’O

Impurities. —This salt is met with in the shops of various degrees ofpurity. If pure, it should dissolve acids without depositing any blackishmatter; it should leave no residuum when heated on platinum or glass;