45 0 
PHARMACEUTICAL MEETING. 
proached even the proposed amended strength, and when this latter is the offi¬ 
cinal one, perhaps those solutions which are now so inferior, will dwindle down 
to something still less. 
The facility, however, with which this amended solution can be made, and 
its much less liability to change (when kept with the proper precautions), will 
leave little room for excuse in supplying the dilute solutions commented upon. 
While this subject is under discussion I should suggest that, in future, the 
directions for the preparation of this solution be somewhat modified; and, in 
doing so, it must not be thought that I for one moment hold the opinion that a 
pharmacopoeia should be an elaborate text-book for a manufacturer, but for the 
reason that it would be advisable, in all cases where processes are given, that a 
pharmacist’s attempt should, without several experiments, result in an approxi¬ 
mation to that perfection intended by the compilers. 
The phrase “ pass into it ( i . e. the magnesia apparatus) pure washed carbonic 
acid ” would, I think, be better rendered as force into it, and for this reason :— 
For the gas to pass freely (other than by diffusion) the pressure in the gas¬ 
holder must be greater than that in the cylinder in which the solution of the 
precipitated carbonate is to be effected, and the pressure in the generator 
greater than that in the gas-holder. Such an arrangement would be unneces¬ 
sarily expensive and inconvenient. 
It is customary to introduce the gas into the cylinder by means of a force 
pump, and there retain it under pressure by a check-valve. The word “ force, ’ 
therefore, to my mind, would give a more complete idea of this part of the pro¬ 
cess than the word “pass,” 
I would also suggest that, after the phrase “ retained there under pressure , 
the words of “ about three atmospheres ” be inserted ; in fact, directions similar 
to those given in the Pharmacopoeia for lithia and soda waters. 
This point is important, inasmuch as the quantity of magnesia dissolved under 
various pressures differs considerably. For instance, that made with the offici¬ 
nal proportions, under a pressure of one atmosphere, will contain about five 
grains of carbonate to the fluid ounce ; while that made under greater pressure 
will contain nearly the whole of the carbonate of magnesia (16*9 grs. to the fluid 
ounce) produced from the sulphate ordered, as the table appended will show. 
This addition would, I think, be more likely to ensure uniformity of the fluid 
when it reached the hands of the public. 
In conclusion, I would remark that the twenty-four hours’ contact with car¬ 
bonic acid is by no means necessary, although undoubtedly the most economical 
for the production of a solution of the B. P. strength, for it can be accomplished 
in as many minutes if the pressure be increased to fifteen or twenty atmospheres, 
and the directions of the Pharmacopoeia somewhat modified. 
Fluid Magnesias of Pharmacy, December, 1869. 
Calcined Magnesia,* 
MgO. 
Garb, of Magnesia 
(Mg C 0 3 ) 3 MgO, 5 HjO). 
No 
1 
1 fl. oz. 
2*4 
5*7 
2 
11 
4*4 
10-5 
5) 
3 
11 
3*7 
8*8 
11 
4 
11 
4*0 
9*5 
11 
5 
»> 
2*1 
5*0 
11 
6 
fl 
4*4 
10*5 
11 
7 
1 ” 
2*7 
6*4 
* 2*387, factor to convert MgO into (MgC0 3 MgO, 6 H 2 0). 
