STAINING CELLO I DIN SECTIONS 287 



When the ahim sohition is at the l)oihii^f-point add the hema- 

 toxyhn sohition. Satisfactory staining sohitions have been obtained 

 by continuing to heat the sohition for about fifteen minutes after 

 so mixing, then setting stain aside for a week to age in a loosely 

 stoppered container before adding a few thymol crystals to act as 

 preservative. A second method is used to make the dye ready for 

 immediate use. In this case, 0.5 gram of yellow oxide of mercury 

 is added as soon as the hematoxylin is added to the alum, and the 

 solution remo^•ed from the heat. The flask is immersed in a larger 

 vessel and cooled as quickly as possible. Before use, in either 

 method of preparation, the solution should be filtered and a few 

 crystals of thymol be added. This is the stock solution and may 

 be kept for long periods in the well-stoppered bottle and improves 

 after several weeks' aging. 



The yellow oxide of mercury employed to ripen the stain does 

 not keep well when dried, so it has to be made at the time of prepa- 

 ration of the solution. To prepare it, make a saturated solution 

 of mercuric chloride by adding about 8 grams of the salt to 100 cc. 

 of water and boil. Add to the saturated sohition thus formed, 

 about 40 grams of potassium hydroxide. A heavy precipitate is 

 formed. Filter the solution and retain the precipitate, then wash 

 the precipitate with distilled water until no chlorine can be detected 

 when silver nitrate is added to the water that has passed over the 

 mercury precipitate. This yellow paste may be kept if the filter 

 paper upon which it is deposited is kept immersed in water. When 

 added to the hot hematoxylin mixture it is necessary to merely 

 approximate the weight of the paste but excess should be avoided. 



The stock solution may be diluted with equal or twice its volume 

 of water before use, depending upon the time sections are to be left 

 to stain. 



Heidenhaiiis Hematoxylin . — In this method of staining, the 

 mordant and dye are kept separate, not mixed, as in the case of 

 Harris's hematoxylin. Two solutions are prepared. Solution A is 

 made by dissohing 4 grams of crystals of ferric alum (iron ammo- 

 nium sulphate) in 100 cc. of distilled water. Solution B is prepared 

 by dissolving 10 grams of certified hematoxylin crystals in 100 cc. 

 of 100 per cent ethyl alcohol and then allowing to age, for several 

 weeks at least, in a loosely stoppered container. This stock solution 

 of hematoxylin should be diluted with water to 0.5 per cent for use 

 in staining. Allowing the dilute solution to stand before using 

 increases its eftectiveness. For de-staining the stained sections a 

 2 per cent solution of the mordant may be used. 



