724 
THE CODEX AND THE BRITISH PHARMACOPffilA. 
retort, furnished witli a glass-stoppered tube, place the retort upon a furnace, 
and adapt to it a tubulated flask or receiver, to which is adjusted a long tube to 
allow the escape of uncondensed vapours. The phosphorus being then cut into 
pieces of a gramme or more, introduce one of these pieces into the acid mixture 
through the tube into the retort, and heat gently until it is decomposed and dis¬ 
solved ; throw in then, by means of a pair of pliers, another piece of phosphorus, 
taking care to close quickly the tube, and so continue until the whole of the phos¬ 
phorus has been submitted to the action of the nitric acid and has completely 
disappeared in the liquid. Each time that a fresh piece of phosphorus is intro¬ 
duced, effervescence occurs ; the fire should be slackened if it is found too strong. 
When all the phosphorus has thus been disposed of, the liquid which has passed 
over into the receiver is to be returned to the retort, and then a second distilla¬ 
tion is to take place, the effect of which is to complete the action of the nitric acid 
and to ensure the entire transformation of the phosphorus into phosphoric acid : 
then withdraw the liquid from the retort, and concentrate it in a platinum 
capsule, to the consistence of thick syrup, so as to drive off* all the nitric acid ; 
the residue is then diluted with water, so that the solution shall mark 1,45 of 
the densimeter. It is in this concentrated state that phosphoric acid is employed 
for medical use. This acid is much stronger than the acid of the P. B., which 
has a density 1-08. AVhilst it is difficult to see the advantage of having so strong 
an acid, one cannot fail to appreciate the completeness of tlie directions. 
24. Eau Begale. 
A.clde NUro-miiriatique. Aqua regalis. Nitromiiriatic Acid. * 
This is a strong acid, and for pharmaceutical or medicinal purposes much less 
convenient than the dilute acid of the P. B. 
Acide Cyanhydeique. HCy = 27. 
2G. Acide Prussique Medicinal'*. 
Acidu'.n Cyanliydriciim Aqua SohiUim. Aledicinal Prussic Acid. Cyan- 
liydric Acid dissolved in Water. 
Cyanide of Mercury.One hundred grammes, ICO 
Hydrochlorate of Ammonia .... Forty-five grammes . 45. 
Hydrochloric Acid at IT 7 . . . . Ninety grammes . . 90. 
In making this acid the form by which it is prepared resembles that of Gay- 
Lussac, the resulting product being much stronger than that of the P. B., con¬ 
taining 10 per cent, of real acid against two ; from a medicinal and dispensing 
point of view, it is difficult to discover the advantage of having so strong a pre¬ 
paration ; on the contrary, it seems to be an evident disadvantage, more poi¬ 
sonous, more likely to be decomposed, and requiring further dilution before it 
can be dispensed wdth convenience or comfort. 
The following observations are from the Codex ;—The cyanhydric or hydro¬ 
cyanic acid is excessively destructive or poisonous. It is very volatile and very 
liable to change. It should be preserved in stoppered bottles, and sheltered from 
the light. As in spite of these precautions it changes soon enough, it is indis¬ 
pensable that it should be tested from time to time, and that it should be re¬ 
newed when no longer of the strength indicated. 
CHAPTER III. 
METALLIC OXIDES. 
Crystallized oxide of antimony, precipitated oxide of antimony, washed dia¬ 
phoretic antimony or potassic superstibiate (this does not represent our tartar 
emetic), hydrated antimonic acid, red oxide of mercury, red oxide of iron,safran 
de mars aperitif, or hydrated oxide of iron, hydrated peroxide of iron, black oxide 
