CORROSION, DECALCIFIOATION, ETC. 325 



566. Picric Acid should be taken saturated, and changed frequently. 

 Its action is weak. 



Picro-sulphuric acid should of course be avoided on account of the 

 formation of gypsum. 



Picro-nitric or Picro-hydrochloric Acid. MAYER points out that their 

 action is very rapid, and that the copiously evolved C0 2 often produces, 

 mechanically, lesions in tissues; so that in many cases chromic acid is to be 

 preferred, the more so as it more effectually hinders any collapsing of the 

 structures that might result from the withdrawal of their supporting cal- 

 careous elements. 



567. Phosphoric Acid. 10 to 15 per cent. (HAUG, loc. cit. in 559). 

 Somewhat slow, staining not good. 



568. Lactic Acid. 10 per cent, or more. Fairly rapid, preserves well, 

 and may be recommended (HAUG, loc. cit.). 



569. Chromic Acid is employed in strengths of from O'l per cent, to 

 2 per cent, (but see 559), the maceration lasting two or three weeks (in 

 the case of bone). It is better to take the acid weak at first, and increase 

 the strength gradually. In any way the action is extremely slow, and it is 

 therefore better to take one of the mixtures of chromic acid with a more 

 energetic agent. 



570. Chromic and Nitric Acid. FOL takes 70 volumes of 1 per cent, 

 chromic acid, 3 of nitric acid, and 200 of water (Lehrb., p. 112). 



Even with the addition of nitric or hydrochloric acid the action is exces- 

 sively slow, frequently requiring months to be complete. 



571. Chromo-aceto-osmic Acid (VAN VEB STRICBT, Arch. Biol., 

 ix, 1889, p. 29; and SCHAFFEK, Zeit. f. wiss. Mik.,'x, 1893, 

 p. 179). Objects to be left in it for months, the liquid being 

 changed at first every two days, afterwards less frequently. 

 Structure well preserved. 



572. Arsenic Acid. 4 per cent, aqueous solution, used at a tempera- 

 ture of 30 to 40 C. (SQUIBE'S Methods and Formulae, etc., p. 11). 



573. Phloroglucin with Acids (ANDEEK, Centralbl. f. d. med. 

 Wiss.., xii, xxxiii, pp. 193, 579 ; Intern. Monatsscnr., i, p. 350 ; 

 Zeit. f. wiss. Mik., 1885, pp. 375, 539 ; Journ. Boy. Mic. 

 Soc., 1887, p. 504; HACG, Zeit. f. wiss. Mile., viii, 1, 1891, 

 p. 8; FERBERI, ibid., ix, 2, 1892, p. 236; Bull. R. Accad. 

 Med. di Boma, 1892, p. 67). This is the most rapid method 

 of any. Phloroglucin by itself is not a solvent of lime salts ; 



