The regular diluent for powdered drugs dispensed in very small quantities is sugar of milk. Of drugs in tablet form, the tablet triturates are made with sugar of milk, hypodermatic tablets with cane-sugar, and compressed tablets without any diluent except in a few cases where it is necessary to increase the cohesive properties of the powder.

For pills, the ingredients must be worked together into a mass, which is then divided equally into the requisite number of parts. These parts are then given a round or elliptic shape. The pills must be plastic, to permit their shaping, but they must be firm enough to retain their shape on standing.

An excipient is a substance employed to give proper consistence to a mass. It may be water, glycerin, glucose, syrup, glycerite of starch, extract of gentian, etc. The choice of excipient should be left to the pharmacist. For oxidizing substances, as silver nitrate or potassium permanganate, the diluent should be an inert powder, such as kaolin, and the excipient an inert substance, like petrolatum.

Pills may be rolled in some powder, such as starch or lyco-podium, to prevent their sticking together, or they may have a special coating. The more common coatings are gelatin, sugar, and silver. Pills intended to pass through the stomach unchanged, but to disintegrate in the intestine, are known as "enteric" pills, and are usually coated with salol or keratin. These coatings are insoluble in the acid gastric juice, but dissolve in the alkaline intestinal contents. The so-called chocolate-coated pills are really only gelatin or sugar-coated pills with chocolate color. The objects in coating pills are: to improve their appearance, to improve their keeping qualities, to hide their taste, or to make them "enteric."

To hide a bitter or unpleasant taste, powders may be dispensed in liquid form with syrup or other flavoring material, or may be made into capsules, cachets, or coated pills. Drugs of sticky consistence, such as extracts, may be made into a mass, divided into the requisite number of parts, and then put into capsules.

Tablet triturates have sugar of milk as a basis, and their solubility or power of disintegration depends on that of the sugar of milk. They can, therefore, be swallowed whole without fear of non-disintegration. They are best suited for those metallic and alkaloidal salts of which the dose is very small. Extracts and other vegetable materials should be used in tablet triturates only in very minute quantity. Tablet triturates for diabetics may be made with some non-carbohydrate. Hypodermic tablets are usually made with cane-sugar to insure ready solubility, but they readily become broken on handling.

Compressed tablets vary in hardness according to the degree of compression to which they have been subjected, and in solubility according to the nature of the drugs of which they are made. Compressed tablets of readily soluble substances, as ammonium chloride or potassium iodide, should be dissolved in water before taking, or taken with a copious draft of water. If made of substances that are insolubleor soluble with difficulty, as bismuth subnitrate or phenacetin, they should be broken up before swallowing.

(For other solids see Definitions, Part I.)