CORROSION, DECALCIFICATJON, ETC. 323 



of the acid may be taken and have dissolved in it 10 to 15 

 per cent, of common salt. Or (WALDEYER) to a T -jrou P er 

 cent, solution of chloride of palladium may be added y 1 ^- of 

 its volume of HC1. 



Chromic acid is also much used, but has a very weak de- 

 calcifying action and a strong shrinking action on tissues. 

 For this latter reason it should never be used in solutions of 

 more than 1 per cent, strength, and for delicate structures 

 much lower strengths must be taken. 



Phosphoric acid has been recommended for young bones. 



Acetic, lactic, and pyroligneous acids have considerable 

 decalcifying power, but cause great swelling. Picric acid 

 has a very slow action, and is only suitable for very small 

 structures. 



560. Nitric Acid (Buscn, loc. cit.). To all other agents 

 BUSCH prefers nitric acid, which causes no swelling and acts 

 most efficaciously, whilst at the same time it does not 

 injuriously attack tissue-elements. 



One volume of chemically pure nitric acid of sp. gr. 1'25 

 is diluted with 10 vols. water. It may be used of this 

 strength for very large and tough bones ; for young bones it 

 may be diluted down to 1 per ceut. 



Fresh bones are first laid for three days in 95 per cent, 

 alcohol ; they are then placed in the nitric acid, which is 

 changed daily, for eight or ten days. They must be removed 

 as soon as the decalcification is complete, or else they will 

 become stained yellow. When removed they are washed 

 for one or two hours in running water and placed in 95 per 

 cent, alcohol. This is changed after a few days for fresh 

 alcohol. 



Young and foetal bones may be placed in the first instance 

 in a mixture containing 1 per cent, bichromate of potash and 

 y 1 -^ per cent, chromic acid, and decalcified with nitric acid of 

 1 to 2 per cent., to which may be added a small quantity of 

 chromic acid (j 1 -^ per cent.) or bichromate of potash (1 per 

 cent.). By putting them afterwards into alcohol the well- 

 known green stain is obtained. 



561. Nitric Acid and Alcohol. 3 per cent of nitric acid in 

 70 per cent, alcohol. Soak specimens for several days or 



