78 CARMINE STAINS. 



niacal solutions, then the neutralised ammoniacal solutions, then other neutral 

 solutions, including alum and picro-carmine, and borax -carmine. These last 

 requiring a treatment of the tissues with an acid to fix the stain, lead natu- 

 rally to the last group, the acid stains. The alcoholic group is too small to 

 require subdivision. 



133. Hints. Tissues to be stained must be freed from acids before being 

 put into the staining fluid. Overstains may in all cases be washed out with 

 weak HC1. (e. g. O'l per cent.). All carmine stains, with the exception of 

 aceto-carrnine, are permanent in balsam. Aqueous mounts should be acid 

 (except for alum- carmine), and the best plan is to let the mounting medium 

 contain 1 per cent, of formic or acetic acid. Formic acid is to be preferred. 



Remember that none of Grenadier's fluids can be used with calcareous 

 structures that it is wished to preserve. 



Grenadier's alcoholic borax-carmine may be recommended to the beginner 

 as being the easiest of these stains to work with. 



A. AQUEOUS CAEMINE STAINS. 

 a. Alkaline. 



134. Ammonia- Carmine (BE ALE, How to Work, fyc., p. 109, 

 4th ed.). 



Carmine . . . . . .10 grains. 



Liquor Ammonias (fortissimus, B.P.) . | drachm. 

 Price's glycerin ..... 2 ounces 



Distilled water . . . . 2 



Alcohol ...... J ounce 



The carmine, in small fragments, is to be dissolved in the 

 ammonia, with the aid of heat. Boil for a few seconds, ;nd 

 let cool. Leave uncorked for at least an hour, or until i lie- 

 excess of ammonia has evaporated, as tested by the smell. 

 Then add the glycerin, water, and alcohol, and filter, or allow 

 to settle and decant. If after keeping for some months the 

 carmine begins to precipitate, owing to the escape of ammonia, 

 add one or two drops of liquor ammonias. 



Another formula, given by Beale for the special purpose of 

 staining by means of injection, will be found at p. 304 of the 

 same work. 



135. Simple Aqueous Ammonia-Carmine. The simple solu- 

 tion of carmine in aqueous solution of ammonia is not stable, 

 but from the very moment of its formation is engaged in \\ 

 series of chemical changes, <t which the nature is still imper- 

 fectly understood, though it is now known that they are due, 

 in part at least, to the growth ol ;i speeinl microphyte. They 



