DECALCIFICATION 251 



cent, solution of chloride of palladiurn may be added j'^ of its 

 volume of HCl. 



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

 action and a strong shrinking action on tissues. For this 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 decalci- 

 fying power, but cause great swelling. Picrid acid has a very 

 slow action, and is only suitable for very small structures. 



591. C. E. Jenkin's Decalcifying and Dehydrating Fixative 

 {Journ. Path. Bad., vol. xxiv, 1921). 



Hydrochloric acid ..... 4 



Glacial acetic acid ..... 3 



Chloroform ...... 10 



Water ....... 10 



Absolute alcohol ..... 73 



Immerse tissue in 100 times its volume of the solution. The 

 formula is based on Carnoy's fluid, and avoids the yellow colour 

 given by the nitric acid agents, and gives a very good stain with 

 ha'matoxylin. Wash out in absolute alcohol, several changes. 



This fluid acts rapidly, a piece of human rib softening in forty- 

 eight hours. 



592. Nitric Acid (Buscn, loc. cit.). To all other agents Busch prefers 

 nitric acid, which causes no swelhng and acts most efficaciously. 



One volume of chemically pure nitric acid of sp. gr. 1-25 is diluted 

 with 10 volumes 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 cent. 



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

 they are then placed in the nitric acid, ivhich 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 ^^ 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^ per cent.) or 

 bichromate of potash (1 per cent.). By putting them afterwards into 

 alcohol a green stain is obtained. 



593. Nitric Acid (Schaffer, Zeit. iviss. Mik., xix, 1903, p. 460). 

 SciiAFFER also finds nitric acid the best reagent. It should be taken 

 pure ; the addition of formol, alcohol, or the like, slows the reaction. 

 The best strength is from 3 to 5 per cent. Objects must not be washed 

 out directly with water, and washing in salt solution, alcohol, phloro- 

 glucin, or formol, is not sufficient to prevent swelling. Alum in 5 per 

 cent, solution is good, but not necessary. Material should be well fixed 

 and imbedded in celloidin (§ 182) ; harden in alcohol ; remove the 

 alcohol with water ; put for twelve to twenty-four hours (large speci- 

 mens longer) into nitric acid of 3 to 5 ])er cent., then into a 5 per cent, 

 solution of sulphate of lithium or sodium, to be changed once in the 



