FIXING AND HARDENING AGENTS. 59 



picro-sulphuric acid. I myself consider it distinctly superior to picro- 

 siilphuric for most things. 



98. Piero-hydroehloric Acid (Maybe, ibid.). — 



Water 100 vols. 



Hydi-ocUoric acid (of 25 per cent. HOI) . 8 „ 

 Picric acid, as mucli as will dissolve. 



99. Picro-chromic Acid (Fol, Lehrh., p. 100). — 



Picric acid, sol. sat. in water . . 10 vols. 



1 per cent, chromic acid solution . . 25 ,, 



"Water . . . . . . 65 „ 



I have seen Fol's formula, with the addition of a trace of 

 acetic acid, quoted as "liquid of Haensel." 



Lo Bianco takes equal parts of picro-sulphuric acid and 

 chromic acid of 1 per cent. 



Rawitz [Leitfaden, 1895, p. 24) takes 1 part of picro-nitric 

 acid, and four parts 1 per cent, chromic acid. Wash out in 

 70 per cent, alcohol. 



100. Piero-osmie Acid. — Flemming {Zells. Kern u. Zellth., p. 381) 

 has experimented with mixtures made by substituting picric for chi-omic 

 acid in the chromo-osmic mixtures (§ 42), and finds the results identical, 

 so far as regards the fixation of nuclei. The fixation of cytoplasm is in 

 my preparations decidedly inferior. 



0. VOM 'RATuKAnat. Anz., xi, 1895, p. 289) adds to 200 c.c. of saturated 

 aqueous solution of picric acid, 12 c.c. of 2 per cent, solution of osmic 

 acid, and 2 c.c. of glacial acetic acid. 



Rawitz (Leitfaden, p. 24) takes picro-nitric acid, 6 vols. ; 2 per cent, 

 osmic acid, 1 vol. Fix for i to 3 hours. Transfer direct to 70 per cent, 

 alcohol. 



101. Picro-platinie and Piero-platin-osmio Mixtures. — O. voM 

 Bath {toe. cit., last §, pp. 282, 285) makes a pioro-platinic mixture with 

 200 c.c. saturated aqueous solution of picric acid, 1 g. of platinic chloride 

 (dissolved in 10 c.c. of water), and 2 c.c. of glacial acetic acid. 



The picro-platin-osmic mixture, which is, in my opinion, much 

 superior, is made by adding to the foregoing 25 c.c. of 2 per cent, osmic 

 acid. 



Other PiCEic Mixtures. See §§ 70 and llO to 112. 



Other Fixing and Hardening Agents. 



102. Alcohol. — For fixing only two grades of alcohol should 

 be employed — very weak, or absolute. Absolute alcohol 



