DECALCIFICATION, DESILICrFICATION, AND BLEACHING. 281 



in a mixture containing 1 pei' cent, bicliromate of potash and 

 Yo" per cent, cliromic acid, and decalcified with nitric acid of 

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

 chromic acid {~ per cent.) or bichromate of potash (1 per 

 cent.). By putting them afterwards into alcohol a green 

 stain is obtained. 



557. Nitric Acid (ScHAFtEi;, Zeit. wiss. Mik., xix, 1903, 

 p. 460). — ScHAFFEE 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, phloroglucin, 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 (§ 554) ; harden in 

 alcohol; remove the alcohol with water; put for 12 to 24 

 hours (large specimens longer) into nitric acid of 3 to 5 per 

 cent , then into a 5 per cent, solution of sulphate of lithium 

 or sodium, to be changed once in the course of 12 to 24 

 hours ; running water, 48 hours ; alcohol. 



558. Nitric Acid and Alcohol. — 3 per cent, of nitric acid in 

 70 per cent, alcohol. Matee has long used 5 per cent, acid 

 in 90 per cent, alcohol. Soak specimens for several days 

 or weeks. Pure nitric acid, even if weak, readily exercises 

 a gelatinising action on bone ; whilst the addition of alcohol 

 (or of alum) counteracts this action (Fish, Ref. Handb. Med. 

 Sci., Supp., p. 425). 



Thoma {Zelt. iziss. Mik., viii, 2, 1891, p. 191) takes five 

 vols, of 95 per cent, alcohol and 1 volume pure concentrated 

 nitric acid. Leave bones in this mixture, changing the liquid 

 every two or three days, until thoroughly decalcified, which 

 should happen, even with large bones, in two or three weeks. 

 Wash out until every trace of acid is removed (^. e. for some 

 days after no acid reaction is obtained with litmus paper) in 

 95 per cent, alcohol containing an excess of precipitated 

 carbonate of lime. This may take eight to fourteen days, 

 after which the tissues will stain well and may be treated as 

 desired. 



