114 H^EMATEi'N AND OTHER ORGANIC STAINS. 



In face of the very great advantages offered by the mode 

 of preparation worked out by MAYER I have no hesitation in 

 saying that the old methods ought to be entirely discarded, 

 and Mayer's formulae only, or at least only such formulae as 

 conform to the principles laid down by him, used instead. If 

 this be done the methods of Unna will come to be of but 

 secondary importance ; but they may still be occasionally 

 useful, and for that reason, as well as for their theoretical 

 interest, I proceed to set them out in the following paragraphs. 

 For MAYER'S haematein methods see 179 et seq. 



175. UNNA'S Ripening Method (Zeit. f. wiss. Mik., viii, 4, 

 1892, p. 483). It has been explained above that the sponta- 

 neous "ripening" of haematoxylin solutions is due to the 

 absorption by them of oxygen from the air, and the conse- 

 quent oxidation of their haematoxylin into haematein. UNNA 

 has found (as MAYER had found before him) that a freshly 

 prepared light red alum solution of hsematoxylin can be in- 

 stantly ripened that is, converted into a dark blue solution 

 of haematein of even much greater staining power than spon- 

 taneously ripened solutions by the simple addition of a little 

 neutralised peroxide of hydrogen. Such an instantaneously 

 ripe solution may be conveniently prepared as follows : 

 Make a solution of crystallised haematoxylin in alcohol, and 



' another solution of about five times as much alum in water, 

 and mix the two solutions in a test-tube. Then pour a little 

 commercial peroxide of hydrogen solution into a watch-glass, 

 and add a crystal of soda. Eemove the soda as soon as a 

 blue litmus paper remains blue in the solution, pour the solu- 

 tion into the test-tube, and heat for a moment over 'a flame. 

 The staining bath is now ripe, and must be used for staining 

 at once, as precipitation of the haematein begins to set in the 

 moment the state of ripeness is attained. 



176. UNNA'S Half -ripe Constant Stock Solution (ibid.). It is 

 inconvenient to have to make a fresh solution of haematoxylin 

 every time it is desired to prepare a ripened solution for 

 staining. Unna, therefore, sought for a means of preventing 

 the continuance of spontaneous oxidation of hasmatoxylin 

 solutions, which, as explained above, leads in course of time 

 to over-ripeness. The spontaneous oxidation being arrested at 

 any desired stage, a constant half-ripe solution is obtained, 



