14 
THE CODEX AND THE BRITISH PHARMACOPOEIA. 
BY A. F. HASELDRN. 
{Continuedfrom p. 726.) 
43. Eau de Chaux. 
Oxydum Calcicum Aqua solutum. 
A solution of calcic oxide in water, Lime-water. 
Quicklime. q. v. (as much as you wish). 
Distilled water. q. s. (a sufficiency). 
Place the quicklime in a pan of brown stoneware and sprinkle it with water, 
which should be allowed to fall a little at a time and in the shape of a very 
small stream, so that it may be absorbed and solidified; the mass becomes heated, 
disengages abundant watery vapours, splits up, and becomes transformed at last 
into a very fine white powder, known as slaked lime or hydrated lime. 
Put into a large jug or bottle a portion of this powder, and shake it with 
thirty or forty times its weight of water, to take from it the potash which it 
contains ; allow it to settle,pour off the liquor, which reject, then pour upon the 
powder which remains at least one hundred times its weight of distilled water ; 
leave together for some hours, taking care to agitate from time to time, then 
allow it to settle. 
This clear liquor, decanted, constitutes lime-water ; it contains in a litre, at a 
temperature of 15°, T285 gr. of caustic lime in solution, about half a grain to 
the ounce. It rapidly absorbs carbonic acid from the atmosphere, and becomes 
covered with a thin film of carbonate of lime. It should be kept in bottles well 
stoppered, and, for greater certainty, an excess of uudissolved lime should be 
left in the bottles; care should be taken to separate this excess by filtration at 
the time of using it. 
Lime-water thus prepared still retains traces of chlorides, which the previous 
washing has not completely removed ; it would therefore be unfit for certain 
preparations, such as the oxide of silver ; to have lime-water free from chlorides 
the washing should be continued until nitrate of silver produces in the liquor a 
precipitate entirely dissolved by nitric acid. 
Compared with the P. B., and for pharmaceutical purposes, the directions 
seem needlessly minute ; for chemical use it is quite necessary that the precautions 
stated should be taken. 
Potasse, Protoxyde de Potasse Hydrate. KO,HO = 56T. 
44. Potasse Caustique a la Chaux*. 
JPierre a Cautere. Oxydum Potassicum ope Calcis paratum. 
Caustic Potash. Potassic Oxide, prepared by means of Lime. 
This is ordinary caustic potash, either in sticks or blocks, prepared by boiling 
down the caustic solution of potash. The next preparation— 
45. Potasse Pure. 
Potasse a VAlcool. Hydras Potassicus , 
is simply the former substance, purified by solution in alcohol, at 90°, and 
evaporated ; having recovered a portion of the spirit to be kept for future 
similar purposes. It is singular that liquor potassse, which is thought so much of 
in England, is not in the Codex, but solution of caustic soda, which is stronger 
than the P. B. solution, and described as soapraakers’ lees, has a place. 
CHAPTER IV. 
SULPHIDES. 
These sulphides having no particular interest for the pharmaceutist, I think 
