CORROSION, DECALCIFICATION, ETC. 329 



582. Nitric Acid. PAEKEE (Bull. Mus. Comp. Zool, Cambridge, 

 U.S.A., 1889, p. 173 ; see Zeit. f. wits. Mik., viii, 1, 1891, p. 82) says that 

 for eyes of scorpions the usual 5 to 10 per cent, solutions are not strong 

 enough. He treats sections, fixed to the slide with SCHALLIBAUM'S medium, 

 for about a minute with a solution of up to 50 per cent, of nitric acid in 

 alcohol, or, still better, with a 35 per cent, solution of a mixture of equal 

 parts of nitric and hydrochloric acid in alcohol. To make the solution, the 

 acid should be poured slowly into the alcohol (not vice versa), and the 

 mixture kept cool. 



JANDEE (Zeit. f. wiss. Mik., xv, 2, 1898, p. 163) takes for removal of 

 pigments FOL'S chromo-nitric acid ( 570) ; twelve to forty-eight hours is 

 enough for small objects. 



584. Caustic Soda. RAWITZ (Leitfaden, p. 29) dissolves the pigment 

 of the mantle of Lamellibranchiata by means of 3 to 9 drops of officinal 

 caustic soda solution added to 15 to 20 c.c. of 96 per cent, alcohol. 



