For dried sulphate of iron, of which a large quantity is sometimes ordered in a pill, I find syrup the best excipient. By this means 5 grains of this can be thus made into a pill.[106]
[106] ‘Pharmaceutical Year Book.’
It may be further remarked, that no deliquescent salt should enter into the composition of pills not intended for immediate use; and that when efflorescent salts are so employed they should be first freed from their water of crystallisation.
When the mixed ingredients are made into a mass (pill-mass), which it is not intended at once to divide into pills, it should be preserved in a piece of bladder or gut-skin placed in a covered stoneware or earthenware pot. In this state it may be occasionally moistened with a little weak spirit to prevent its getting hard.
The weight (size) of pills varies from 1⁄2 gr. to 6 gr. If heavier than this, they are called ‘boluses.’ Formerly, as a general rule, they were made of 5 gr. each; but pills of this weight are, in general, so large that some persons find a difficulty in swallowing them. Another disadvantage of large pills is the trouble of nicely apportioning the dose,—one pill being, perhaps, too small a quantity, and two pills the reverse. Hence, 2 to 3-gr. pills are now the favourite size with both pill-takers and dispensers, notwithstanding that 5-gr.
pills are still ordered in one of the authorised Pharmacopœias.
Pills are occasionally coated with gold, silver, and other substances, to render them more agreeable to the eye, or to prevent the taste of nauseous ingredients affecting the palate during deglutition. They are gilded and silvered by placing them, in the moist state, on a leaf or two of the metal in a small gallipot, and covering them in a similar manner with another leaf of metal; over the mouth of the gallipot is laid a piece of smooth writing paper, and on this the palm of the hand; a sudden and rapid circular motion is then given to the whole. If the pills are not sufficiently moist or sticky, they should be rendered so by rolling them between the fingers very slightly moistened with mucilage, before proceeding to silver them. Another method is to shake them in a similar manner with a little gold or silver dust.
Mr Haselden recommends a varnish composed as follows:—Resin[107] of tolu, 3 parts; rectified spirit, 6 parts; methylated ether, 2 parts. Well shake until all that will is dissolved. Use the clear solution. Mr Hasleden says iodide of iron pills are well preserved by this coating, and also granules of secale cornutum.
[107] This is the substance which is left in the preparation of syrup of tolu.
When pills are to be covered with gelatin, each pill, being stuck on the point of a very thin wire four or five inches in length, is dipped into a solution of gelatin, so as to coat it completely, and the wire is then inserted into a pin-cushion, or a vessel containing fine sand, and left until the gelatin is firm, which occurs in about a quarter of an hour; the pins may then be easily removed by simply warming them, by placing the centre of each wire for a second or two in the flame of a spirit lamp or candle. ‘Sugar-coated pills’ are prepared in nearly the same way, but substituting hot and highly concentrated syrup, to which a little gelatin has been added, for a simple solution of gelatin.