When die and punches are to be removed, take out the upper punch first, then the lower punch and die, which may come out suddenly and be injured by knocking against the upper punch if the latter be still in place.
When particles of the powder stick to the die or punches, they should not be scraped off with a hard instrument, as this is liable to scratch, but should be wiped off with a soft, slightly moistened cloth. To prevent sticking, a little talcum may be used, sprinkled over the powder and lightly mixed by stirring with a spatula.
When the upper face of the tablet splits off, we speak of "capping." To overcome this, ten per cent. of fat starch may be added to the powder. Should "capping" still occur, the amount of fat starch might be increased. "Capping" may also be due to the use of excessive pressure. It may furthermore be due to die or punches being worn or damaged. When this has occurred, the best thing to do is to get a new set of punches, or to have the damaged one refinished by an expert mechanic, preferably the makers of the tablet machine.
It would lead us beyond the scope of this work to give detailed directions for making tablets of all kinds. A pharmacist who has equipped himself with a tablet machine and has developed the ambition to make a general line of tablets[7] may be referred to Mr. Joseph R. Wood's book[8] on this subject.
CHAPTER VI.
THE CONSTRUCTION OF FORMULAE FOR SWEET TABLETS.
Choice of Flavor.
THERE are quite a number of medicines sufficiently free from taste and odor to be made perfectly pleasant by the mere admixture of sugar and of flavoring. These can, of course, be prepared with any flavor desired. In the formulary, rose has been chosen as the flavor under these circumstances, but any other flavor may be used instead.
Substances that have a slightly acrid taste are generally best disguised by peppermint. For sour taste, lemon is best. Wintergreen was chosen as the flavor for salicylates.