1888.] Dr Woodhead on Mercuric Scdts as Antiseptics. 241 
out that this holds good only where weak solutions (1 to 1000 of 
the bichloride in this instance) are used. 
If 1 c.c. citric acid he used in place of the above, there is first a 
slight opacity which soon disappears, the fluid becoming slightly 
darker. After twenty-four hours the precipitate occupies one-fifth 
of the column, and the supernatant fluid is very dark, almost the 
colour of porter. The whole of the hfemoglobin is reduced. 
With 3 drops of hydrochloric acid the fluid is turned muddy for 
a short time, and then it rapidly turns dark brown (again almost 
the colour of porter). At the end of twenty-four hours there is a 
precipitate which occupies two-fifths of the column. There are no 
haemoglobin absorption bands, but much closing in at the two ends 
of the spectrum. 
If only a single drop of hydrochloric acid be used, the fluid is 
darkened for a few seconds only, it then suddenly clears up almost 
completely, ilext day there is only a slight precipitate; but the 
whole of the haemoglobin is reduced. 
If before blood is mixed with the bichloride solution a couple of 
drops of liq. ammoniae be added, there is a white band at the point 
of contact, insoluble in excess of ammonia. A dense precipitate is 
ultimately formed, the so-called white precipitate or infusible white 
precipitate. According to Fownes, this is mercurammonium chloride 
(NHIHg"). Cl, which is insoluble in excess of ammonia, but is soluble 
in hot water or with great excess of cold water, when, however, it 
becomes converted into a higher mercuric ammonium chloride. This 
white precipitate, harmless as a germicide, remains in the fluid, and 
it is oiilj’- when acted upon by the heat of the body or by an excess 
of cold water that it can again become active as a mercurial salt, and 
then, naturally, only in very weak solution, in which form it is quite 
possible it may retain feeble antiseptic properties. Lauder Brunton 
states {Pharmacology, 3ded., p. 695) that “ it is used in combination 
as an ointment to destroy parasitic fungi, but more especially to kill 
pediculi in the hair on the body. It is also useful in impetigo con- 
tagiosa, lichen, pityriasis, subacute eczema, and other skin diseases.” 
It is important to bear in mind this action of ammonia on the 
bichloride, for it is found that, if we add blood to the mixture of 
ammonia and bichloride solution, there is no precipitate of albu- 
minate of mercury, or if it is formed, it is very rapidly dissolved. 
