282 PREPARATION OF REAGENTS [ C. H. IX 



for r to 2 minutes then expose to light in water till brown. One may 

 stain afterward with hematoxylin for the nuclei ; mount in glycerin, glycerin 

 jelly or in balsam. 



\ 427. Sudan III for Fat. Sudan III or azo-benzene-azo-/j-napthol, was 

 introduced by Daddi into histology in 1896 (Arch. Ital de Biologic, t. 26. p. 

 142) , as a specific stain for fat. As it is soluble in all forms of fat and oils and 

 in xylene, alcohol, etc., it is impossible to mount specimens in balsam after 

 staining. As the fat of tissues is removed by the reagents used in the paraffin 

 and collodion methods (see Ch. X), only teased, free-hand or frozen sectioned 

 material fresh or fixed in some non-fat dissolving fixer can be used (Miiller's 

 fluid and 5% formaldehyde are excellent). The tissues cut free-hand or with 

 the freezing microtome or teased can then be stained with a saturated alco- 

 holic solution of the Sudan. It stains all fat a brilliant red. Preparations can 

 be preserved in glycerin or glycerin jelly. This stain is largely used in 

 Pathology. 



Daddi used the substance to feed animals and thus to stain the fat which 

 w y as laid down in the body while the Sudan was fed. 



The fat in the body already deposited remains unstained. This substance 

 then serves to record the deposit of fat in a given period. In 1907 Dr. Oscar 

 Riddle fed Sudan to laying hens, and the fat in the layers of yolk laid down 

 during the feeding was stained red (Science, XXVII, 1908, p. 945). For 

 staining the yolks of hens eggs the hen may be fed doses of 20 to 25 milli- 

 grams of the Sudan. Eggs so colored hatch as usual, and the chick in utilix.- 

 ing the colored yolk stains its body-fat pink (Susanna P. Gage). 



\ 428. Table Black. During the last few years an excellent method of 

 dying wood with anilin black has been devised. This black is lustreless, and 

 it is indestructible. It can be removed only by scraping off the wood to a 

 point deeper than the stain has penetrated. 



It must be applied to unwaxed or unvarnished wood. If wax, paint or 

 varnish has been used on the tables, that must be first removed by the use of 

 caustic potash or soda or by scraping or planing. Two solutions are needed : 



SOLUTION A 



Copper sulphate 125 grams 



Potassium chlorate or permanganate 125 grams 



Water looo'cc. 



, Boil these ingredients in an iron kettle until they are dissolved. Apply 

 two coats of the hot solution. Let the first coat dry before applying the 

 second. 



SOLUTION B 



Anilin oil 120 cc. 



Hydrochloric' acid 180 cc. 



Water 1000 cc. 



Mix these in a glass vessel putting in the water first. Apply two coats 

 without heating, but allow the first coat to dry before adding the second. 



