192 
ORIGINAL COMMUNICATIONS. 
Some physicians prescribe the bicarbonate of potassa, instead 
of the common salt of tartar. It does not much alter the cha- 
racter of the medicine; but is to be preferred as making a 
much nicer preparation. The salt of tartar always contains 
silica; and when used in this preparation, the silica exists in 
the form of a flocculent precipitate. This precipitate, though 
entirely inert, might as well be avoided, when it can be so 
easily done. Neutral Mixture is preferred by some practi- 
tioners in the form of the Effervescing Draught. For this, 
the bicarbonate of potassa is certainly to be preferred, as it 
seems that not only the agency of the citrate of potassa is de- 
sired, but likewise that of the carbonic acid gas, which is dis- 
engaged during the action of the acid on the alkali. The rea- 
son why the bicarbonate is to be preferred in this case is very 
evident. The following prescriptions for the Effervescing 
Draught are common. 
1^. Potassae bicarb. 3iij. 
Aquae, §iij. 
Liqua. 
Sig. Haifa table spoon full with as much lemon juice in 
the state of effervescence. 
p. Potassae bicarb. Siij. 
Aquae, giv. 
Liqua. 
Sig. A table spoon full with as much lemon juice in the 
state of effervescence. 
1^. Sal. Tart. 3ij. 
Aquae, §iv. 
The dose of this is the same as that of the last prescription. 
It will not be very difficult to discover the disparity existing 
between these. Having shown the great want of uniformity 
in this preparation, we will proceed to state a few facts fur- 
nished by actual experiment. Lemons yield from f. siij. to 
f. ^iss. of juice. We have been sometimes disposed to think, 
