HAMATE IN 153 



higher oxidation product. We have obtained some good stains 

 with hasmatein, but also some very bad ones ; presumably the 

 solutions easily over-oxidise on contact with the iron salt. 



The hcTematoxylin is generally dissolved in water. Lee fre- 

 quently prefers alcohol, of 50 per cent., as less injurious to 

 tissues. 



The method is a regressive one. It has been proposed to stain 

 progressively, which we have tried, and have had extremely bad 

 results. 



The differentiation requires to be carefully timed. For this 

 reason the method is only applicable to sections, which should 

 be thin, best not over 10 fx. 



Iron haematoxylin is one of the most important of stains. It 

 enables us to stain elements which cannot be selectively stained 

 in any other way. The stain is very powerful, and of a certain 

 optical quality that is peculiarly suited to the employment of high 

 powers ; it will allow of the use of higher eye-pieces than other 

 stains. It will take effect on any material, and is quite per- 

 manent. Further details as to the characters of the stain are 

 given in § 282. 



281. Benda's Later Iron Haematoxylin {Verb. d. Anal. Ges., vii, 

 1, 1893, p. 161). Sections are mordanted for twenty-four hours 

 in liquor ferri sulphurici oxidati, P.G.,* diluted with one or two 

 volumes of water. They are then well washed, first with distilled 

 water, then with tap water, and are brought into a 1 per cent, 

 solution of haematoxylin in water, in which they remain till 

 they have become thoroughly black. They are then washed and 

 differentiated. The differentiation may be done either in 30 

 per cent, acetic acid, in which case the progress of the decoloration 

 must be watched, or in a weaker acid, which will not require 

 watching ; or in the sulphate solution strongly diluted with 

 water. 



We find that if the iron solution be taken for the differen- 

 tiation, it should be taken extremely diluted (of a very jmle 

 straw-colour, about 1 : 30 of water), and the progress of the 

 differentiation watched ; as if it be only diluted about tenfold, for 

 instance, the decoloration is extremely rapid. See also last §. 



Lee found that Benda's mordant is unnecessarily, sometimes 

 harmfully, strong, and that the liquor ferri may be diluted ten- 

 fold with advantage. The duration of the bath in the mordant 

 is also for most purposes excessive as directed by Benda. We 

 find that three to six hours in the solution diluted tenfold is 

 generally sufficient with favourable material. 



* This preparation consists of sulphate of iron, 80 gnis. ; water, 40 ; 

 sulphurie acid, 15 ; and nitric acid, 18, and contains 10 per cent, of Fe. 

 Doubtless the ferri persulphatis liquor B. P. will do instead ; the point 

 is, to have a per-salt, and not a proto-salt. 



