SPECIAL METHODS. 183 



been added, the commercial dry ammonium carminate (the 

 so-called Hoyer's ammonium carminate). Alcohol or acid 

 alcohol is best used for washing. 



4. Sodium carminate can be obtained in solid form, and 

 may be dissolved in an aqueous .5$ solution of ammonium 

 carbonate. 



5. P. Mayer s carmine solution is prepared by rubbing up 

 4 grams of carmine in 15 ccm. of water, then adding 30 drops 

 of hydrochloric acid while warming, and finally adding 95 

 ccm. of 85$ alcohol, boiling, neutralizing with ammonia, and 

 filtering when cold. Is used both for staining sections and 

 for staining in mass. 



6. Carminic Acetate. Ammonium carminate is decom- 

 posed with acetic acid added drop by drop in the least 

 possible excess until the cherry-red fluid has become brick- 

 red, when it is filtered. For washing, a mixture of one part 

 hydrochloric acid in 200 parts glycerine or one of one part 

 formic acid in 100 parts glycerine is recommended. 



7. Picrocarmine is the term applied to variously prepared 

 mixtures of picric acid and carmine. Only the simplest 

 recipe (Hoyer's) need be given here. According to this, 

 pulverized carmine is dissolved in a concentrated solution 

 of neutral ammonium picrate. 



P. Mayer (III) now uses pure carminic acid for the prep- 

 aration of carmine solutions, of which he especially recom- 

 mends the following: 



8. Carmalum is prepared by dissolving i gram of carminic 

 acid and 10 grams of alum in 200 ccm. of distilled water, 

 with heat. The solution may be decanted off or filtered. 

 To protect it against decomposition, this author finall/adds 

 a few crystals of thymol, or .1$ of salicylic acid or .5$ of 

 sodium salicylate. On washing with water the protoplasm 

 remains somewhat colored. To obtain a purely nuclear 

 stain, the washing must be carefully done with a solution of 

 alum or a weak acid. 



9. Paracarmine is prepared according to the following 

 recipe : I gram of carminic acid, gram of aluminium chlo- 

 ride, and 4 grams of calcium chloride are dissolved in 100 



