180 CHAPTER XIT1. 



be obtained in a sufficiently pure state from GRUBLER & 

 HOLLBORN. 



This is somewhat more easily soluble in both water and 

 alcohol than hsematein is, and does quite as well for staining 

 purposes. The histologist can easily prepare it for himself 

 as follows : 



235, Haemateate of Ammonia (MAYER, Mitth. Zool . Stat. 

 Neapel, x, 1891, p. 172). Dissolve 1 grrn. of heematoxylin 

 with the aid of heat in 20 c.c. of distilled water, filter 

 if necessary, add 1 c.c. of caustic ammonia (of 0'875 

 sp. gr.), and bring the purple liquid into a capsule of such 

 dimensions that its bottom be not covered to a depth of more 

 than half a centimetre. Let the liquid evaporate at the 

 ordinary temperature and protected from dust. The dry 

 product will consist of haemateate of ammonia, about equal 

 in weight to the hsematoxylin taken in the first instance. 

 The evaporation should not be hastened by heat, as this may 

 give rise to the formation of substances that are insoluble in 

 alcohol. The preparation should not be touched, until it is 

 dry, with any other instruments than such as are made of 

 glass, porcelain, or platinum. 



236. Characters of the Alumina-Haematein Stains (or of the So- 

 called Alum-Haematoxylin Stains), The alum-haematein lakes 

 stain in different tones of blue or of red, according to the com- 

 position of the staining solution. Neutral or alkaline solutions 

 give a blue stain ; acid solutions give a red one. In order to 

 get a l)lue stain in preparations that have come out red 

 through the acidity of the staining bath, it is a common 

 practice to treat them with weak ammonia, in the belief that 

 the blue colour is restored by neutralisation of the acid that 

 is the cause of the redness. According to MAYER, the 

 ammonia acts not by neutralising the acid, but by precipi- 

 tating the alumina, which carries down the hgematein with 

 it (if no alumina were present the colour would be purple, 

 not blue).* TJie same result can generally be obtained by 

 merely washing out with common tap -water, which is usually 

 sufficiently alkaline (SQUIRE has obtained the reaction with 



* FISCHER, in his Fixirung, Farbung u. Bau des Protoplasmus, pp. 156, 

 157, does not admit this explanation. He proposes another one of a highly 

 speculative nature. 



