54 



FLUID CAUSTICS. 



Hydrochloric, carbolic, and chromic acids act less powerfully 

 than nitric or sulphuric acid. 



Among solid agents, caustic potash exercises a very marked and 

 penetrating action. It can be applied solid or in solution. Sticks 

 of fused caustic are to be preferred. The point is pressed on the 



part to be cauterised 

 until the intended 

 amount of action has 

 been produced. Caustic 

 potash, like some 

 caustics previously men- 

 tioned, acts by abstract- 

 ing moisture from the 

 tissues. It forms a 

 g r e y i s h-y e 1 1 o w scab 

 sometimes mixed with 

 blood. As this scab 

 readily breaks down and 

 becomes fluid, the sur- 

 rounding parts must be 

 carefully protected from 

 its effects. A special 

 caustic is used in Vienna, 

 consisting of six parts 

 of caustic lime and five 

 of caustic potash 

 moistened with alcohol 

 to form a paste, which 

 can. then be applied to 

 the skin to the extent 

 required. This paste 

 does not run or spread. 



Sublimate (perchloride 

 of mercury) is also a 

 powerful caustic. It de- 

 stroys tissues by com- 

 bining with their albumen, and forms a soft grey scab, which 

 afterwards darkens and slowly separates. Sublimate is employed 

 as a powder, paste, or solution. Sublimate collodion consists of 

 five parts sublimate dissolved in thirty parts of collodion. 



Arsenious acid, or white arsenic, is usually employed in the form 

 of paste. The action is slow, the scab firm and durable. 



Fig. 211. — Bud, point, line, and disc firing irons. 



