452 
CAUSTICS. 
Acicl Metallic Caustics . — Mercurial acid; or acid deuto- 
nitrate of mercury, and gold caustic , or Recamier’s caustic, a 
solution of chloride of gold in aqua regia. 
They present properties which show necessarily the pro- 
portion and energy of the elements which constitute them. 
They participate in various degrees in the properties of the 
caustics of the second and third classes, between which, as I 
have already observed, they form the connecting link. They 
nevertheless differ from them in various important points. 
They differ from the purely acid caustics, because they do 
not dissolve fibrine, as they do ; from the neutral metallic 
caustics they are distinguished by the property — which the 
latter do not possess— of perfectly attacking the skin when 
quite dry, and possessing its epidermis. 
Of particular Caustics. 
After having given the general and characteristic proper- 
ties of caustics, considered in analogous groups, we regret 
that our limits will not permit us to enter into the particnlar 
examination of individuals and their destructive properties : 
w T e can only mention a few. 
It is necessary to have ammonia in a state of absolute con- 
centration to have the effect of cauterizing, and even for the 
preparation of Goudret’s vesicant pommade. 
It is advisable to have a little cotton round the pastille of 
potassa at the moment of its application. 
Lime has a great influence in the caustics of Vienna and 
of Filhos. 
The action of monohydrated nitric acid is so rapid that 
there is always reason to fear hemorrhage. 
It is useful to use aqua regia in cases of venomous bites ot 
animals, when other means are not at hand. 
Chloride of bromium will be found to possess all the quali- 
ties of an acid caustic. 
In the long memoir from which this is an extract will be 
found the proportions of Velpeau’s caustic and black caustic, 
and the superiority of the latter over yellow caustic. 
Chloride of antimony becoming decomposed under the 
influence of water, it has an acid reaction, which enables 
this caustic to remove the epidermis. 
There is a revivification of the metals of the last class, 
with their metallic lustre, as far as concerns gold and silver 
caustics, both on the dead and living body. 
It is important to know that 100 grammes of urine decom- 
pose, and in some degree annihilate, on an average, three 
