Characters. - Colourless hard six-sided prisms terminated by six-sided pyramids.

Solubility. - Sparingly soluble in water, insoluble in alcohol.

Reactions. - It decrepitates strongly when heated. Its solution in water gives the reactions showing the presence of potassium and a sulphate (v. p. 595).

Impurities. - Calcium, chlorides, iron and lead.

Test. - The solution should give no precipitate with oxalate of ammonium (no calcium), nitrate of silver (no chloride), nor ammonium sulphide (no metals).

Dose. - 15 to 60 grains.

Preparations

B.P.

Pilula Colocynthidis Composita (p. 522).....................................

1 part in 24.

" " et Hyoscyami (p. 522)...............................

1 " 36.

" Ipecacuanhae cum Scilla (p. 522).......................................

1 " 3.

Pulvis Ipecacuanhae Compositus................................................

4 " 5.

Uses. - Sulphate of potassium is employed as a saline purgative in cases of dyspepsia, biliousness, and albuminuria. It is generally combined with some other aperient, such as rhubarb. From its hardness it is used to aid in pulverising tough vegetable substances, like ipecacuanha in the preparation of Pulv. Ipecacuanhae Co., B.P. It was once supposed to have the power of arresting the secretion of milk, and was therefore given to women who wished to stop suckling.