MOHR AND REDWOOD'S PRACTICAL PHARMACY. 223 
being placed over them, is moved in a circular direction 
with increasing velocity, while a very slight pressure is 
applied. 
" Several substances are used for covering pills, such as 
magnesia, starch, liquorice powder, lycopodium, gold and 
silver leaf, gelatine, and a mixture of gum and sugar. 
The application of these substances to the surfaces of pills is 
intended to prevent their sticking to each other or to the box, 
and also to prevent their being tasted during the act of 
deglutition. 
" Magnesia is very commonly used for covering pills. As 
a light absorbent powder it answers the required purpose 
very well, yet there are some cases in which its use is not 
free from objection. Thus, for instance, if calomel pills be 
covered with magnesia, decomposition will, after some 
time, occur, the mercury being reduced, or oxide formed 
together with muriate of magnesia. Calomel pills that are 
kept ready made should never, therefore, be covered with 
magnesia ; powdered starch might be used in this case. 
" Liquorice powder is sometimes employed in preference 
to magnesia for covering pills, its sweet taste being consi- 
dered advantageous in masking that of the other ingredients 
of the pills. There is, however, a very serious objection to 
the indiscriminate, use of this powder, which arises from the 
fact that, with some persons, it occasions an irritation of the 
fauces, which deprives them of the power of swallowing 
pills which are thus covered. 
" Lycopodium is but little used for covering pills in this 
country. It is extensively employed on the continent, and 
it forms, undoubtedly, the most suitable powder for the 
purpose. It is a light powder, the, particles of which readily 
adhere to the moist surfaces of pills, without becoming them- 
selves moist. It is also free from taste, and has no tendency 
to cause or to undergo decomposition. When lycopo- 
dium is used, it should be applied to the pills on the machine 
or in the finisher, and none of the powder excepting that 
