292 MICROCHEMICAL TESTS 



cent, alcohol) for about ten minutes. The Prussian blue* reaction 

 takes place. Wash in pure 70 per cent, alcohol, dehydrate, clear, 

 and mount in benzol balsam. 



Counter-stain if desired in eosin or safranin (op. cit.). 



Ferrous Salts. As above, substituting ferricyanide of potas- 

 sium instead of ferrocyanide, so-called Turnbull's blue. 



Simultaneous detection of both categories of salts may be 

 made by using a solution of equal parts of ferricyanide and 

 ferrocyanide. 



See also Tirmann, Goerbersdorfer Veroe SentL, ii, 1898, p. Ill ; 

 Schneider, Mitth. Zool. Stat. Neapel, xii, 1895, p. 208 ; Carnoy and 

 Lebrun, La Cellule, xii, 1897, p. 275 ; Sumita, Arch. path. Anat., 

 cc, 1910, p. 230 ; Zaleski, Zeit. Phys. Chemie, xiv, 1890 ; Wassermann, 

 Anat. Hefte, xUi, 1910, p. 283 ; Jones, Biochem. Jour., 1920. 



675. Copper. R. Boyce and W. A. Herdman, in their paper 

 on the Green Leucocytosis in Oysters {Proc. Roy. Soc, Ixii, 1897 — 

 98), have given directions for the application of the well-known 

 potassium ferrocyanide test of chemists, to sections of tissues in 

 which copper is to be detected. These authors fix with proper 

 precautions {vide supra, under " Iron ") in absolute alcohol, imbed 

 in pure paraffin and cut sections. Care must be taken to avoid 

 acid solutions, such as commercial turpentine or old xylol. Sec- 

 tions are brought from absolute alcohol to distilled water, placed 

 in a 1-5 per cent, solution of freshly-prepared potassium ferro- 

 cyanide or, preferably, in equal parts of the same ferrocyanide 

 solution, and a 0-5 per cent. HCl solution, and parts where copper 

 is present go a reddish colour. Sections are then washed in aq. 

 dest., dehydrated in absolute alcohol, cleared in cedar wood oil 

 and mounted in Canada balsam. 



Bromine Test for Copper. Mendel and Bradley (Amer. 

 Jour. Physiol, xiv, 1905) use a concentrated solution of hydro- 

 bromic acid containing a trace of free bromine. Fix as in previous 

 method. Dissolve out paraffin from sections in good xylol, 

 down grade and pass to distilled water. Drain the slide to 

 remove excess water, cover, and introduce a few drops of the 

 hydrobromic acid at the edge. The presence of copper is shown 

 by an intense violet colour. This at once begins to fade and to 

 diffuse throughout the tissue, while the destructive effect of the 

 acid soon obliterates any definite localisation of the metal. 



676. Lead. Frankenberger (Ass. Anat., xvi, 1921), Cretin 

 {ibid., xxiv, 1929) fix in neutral bichromate (Regaud fluid does 



* Prussian Blue [ferric ferrocyanide, Fe4(Fe(CN)6)3] made from 

 potassium ferrocvanide and ferric salts. 



Turnbull's Blue [ferrous ferricyanide (Fe3(Fe(CN)6)2] made from 

 potassium ferricyanide (K3Fe(CN)8) and ferrous salts. Wlien prepared 

 under certain conditions it is practically identical with Prussian blue 

 {Chemical Ency., Kingzett, 1928). 



