Source. - Made from a solution of the Carbonate in distilled water, by passing a stream of carbonic acid gas through it, and purifying the crystals which form.

Characters. - Colourless right rhombic prisms, not deliquescent; of a saline, feebly alkaline taste; not corrosive. 20 gr. neutralise 14 gr. of citric acid, or 15 gr. of tartaric acid.

Dose. - 10 to 40 gr.

Preparation.

Liquor Potassae Effervescens. Potash Water. - Potassae Bicarbonas, 30 gr.; Water, 1 pint. Dissolve, and pass into the solution as much CO2 as it will contain under a pressure of 7 atmospheres.

Dose. - Ad libitum.

b. Liquor Potassse. - Solution of Potash, KHO, (5.84 per cent.) in water.

Source. - Made from a solution of the Carbonate, by boiling with Slaked Lime and purifying. K2CO3 + CaO,H10 = 2KHO + CaCO3.

Characters. - A clear alkaline fluid.

Impurities. - Lime, carbonates, sulphates, and chlorides.

Dose. - 15 to 60 min.

From Liquor Potassae are made: a. Potassa Caustica. - Caustic potash. KHO.

Source. - Made from Liquor Potassae by evaporation.

Characters. - White pencils, hard but very deliquescent, alkaline and corrosive.

Impurities. - The same as of the liquor.

Prom Potassa Caustica is made:

Potassae Permanganas. - Permanganate of potash. KMnO4. See Maganesium.

Source. - Prepared from a mixture of caustic potash, chlorate of potash, and black oxide of manganese, by semi-fusing; then boiling, neutralising with dilute sulphuric acid, and purifying. (1) KC1O3 + 6KHO + 3MnO2 = 3K2MnO4 + KCl + 3H1O. (2) Boiling: 3K2MnO4 + 2H1O = 2KMnO4 + 4KHO + MnO2.

Characters. - Dark-purple slender prisms, inodorous, with a sweet astringent taste. Soluble in 16 parts of cold water. Should be prescribed in simple solution.

Impurities. - Sulphate of potash and oxide of manganese; detected by less solubility in water and volumetric test.

Dose. - 1 to 2 gr.

Preparation.

Liquor Potassae Fermanganatis. - 4 gr. in 1 fl.oz. of distilled water. Dose, 2 to 4 fl.dr.

.Potassii Iodidum. - Iodide of Potassium. KI.

Source. - Obtained by dissolving Iodine in Liquor Potassae, and evaporating - 6KHO+3I2=5KI + KIO3 + 3H1O; then mixing the residue with wood charcoal, fusing, dissolving, and purifying, to convert the iodate, which was formed with the iodide, into iodide - 2KIO3 + 6C = 2KI + 6CO.

Characters. - Colourless opaque cubical crystals, with some odour of iodine, a saline taste, and feebly alkaline reaction; strikes blue with preparations containing starch on addition of chlorine.

Impurities. - Iodate; detected by blue colour with tartaric acid and starch. Free iodine; by starch. And the impurities of the liquor.

Dose. - 2 to 10 gr., or more.

For Preparations, see Iodum.

γ. Potassii Bromidum. - Bromide of Potassium. KBr.

Source. - Obtained from Liquor Potassae, Bromine, and Charcoal, by the same process as the iodide.

Characters. - Colourless cubic crystals, without odour, and of a pungent saline taste. Does not strike blue with preparations containing starch, unless it contain iodide as impurity.

Dose. - 5 to 30 gr.

c. Potasssae Citras. - Citrate of Potash. K3C6H5O7.

Source. - Made by neutralising a solution of Citric| Acid with Carbonate of Potash, and evaporating. 3K2CO3 + 2C6H5O7, H3 = 2K8C6H5O7 + 3H1O + 3CO2

Characters. - A white deliquescent powder, of saline, feebly acid taste.

Dose.-20 to 60 gr.

d. Potassae Acetas., - Acetate of Potash. KC2H3O2. Source. - Made by dissolving Carbonate of Potash in Acetic Acid, evaporating, and fusing the residue. K2CO3 + 2(HC2H3O2) = 2(KC2H3O2) + H1O + CO2.

Characters. - White foliaceous satiny masses, very deliquescent; neutral. The peculiar appearance of thi3 salt is due to crystallisation after fusion.

Impurities. - The carbonate; detected by being insoluble in spirit. Excess of acid; giving acid reaction. Metallic impurities.

Dose. - 10 to 60 gr,

Potassae Acetas is used in preparing:

Tinctura Ferri Acetatis. See Ferrum.

e. Potassae Chloras. - Chlorate of Potash. KC1O3.

Source. - Made by passing Chlorine gas into a mixture of Carbonate of Potash and Slaked Lime (i.e. caustic potash), boiling, evaporating, and separating the chloride of potassium by re-crystallisation. 6KHO + 6C1 = KC1O3 + 5KC1 + 3H1O.

Characters. - Colourless rhomboidal crystalline plates, with a cool, sharp, saline taste. Explodes when rubbed with sulphur. Soluble in 16 parts of cold water.

Impurities. - Chloride of calcium, and lime.

Dose. - 10 to 30 gr.

Preparation. Trochisci Potassae Chloratia. - 5 gr. in each.

f. Potassa Sulphurata. - Sulphurated Potash.

Source. - Made by fusing together Carbonate of Potash and Sublimed Sulphur.

Characters. - Solid greenish masses, liver-brown when recently broken, alkaline and acrid to the taste; a mixture of sulphide, sulphate, sulphite, and hyposulphite.

Dose. - 3 to 8 gr.

Preparation. Unguentum Potassae Sulphuratae. - 1 in 151/2.

2. Potassae Tartras Acida

Potassae Tartras Acida. Acid Tartrate of Potash, Bitartrate of Potash, Cream of Tartar. KHC4H4O6. K Source. - Prepared from argol, the deposit in wine-casks.

Characters. - A white gritty powder, or fragments of cakes, of a pleasant acid taste; not deliquescent. Soluble in 200 parts of cold water.

Dose. - 20 to 60 gr. as a diuretic and refrigerant; 2 to 8 dr. as a purgative.

Acid Tartrate of Potash is an important ingredient of:

Confectio Sulphuris (1 in 9); and Pulvis Jalapae Compositus (9 in 16). It is also used in preparing various other drugs.

From this salt is derived:

Potassae Tartras. - Tartrate of Potash. K2C4H4O6.

Source. - Made by adding Acid Tartrate of Potash to a solution of Carbonate of Potash, and crystallising. 2KHC4H4O6 + K8CO3 = 2K2C4H4O6 + CO2+ H1O.

Characters. - Small colourless deliquescent prisms. 10 parts are dissolved in 8 parts of water.