STAINS AND STAINING 
53 
Alum Carmine. —A 4 per cent aqueous solution of ammonia alum 
is boiled 20 minutes with 1 per cent of powdered carmine. Filter 
after it cools (Lee). 
Stain from 12 to 24 hours and wash in water. No acid alcohol 
is needed, since the solution does not overstain. 
Carmalum (Alum Lake). —Use 1 gram of the powdered stain to 
100 c.c. of very dilute ammonia water. Filter, if there is any 
precipitate. 
Mayer’s Carmalum.— 
Carminic acid. 1 g. 
Alum. 10 g. 
Distilled water. 200 c.c. 
Dissolve with heat; decant or filter and add a crystal of thymol 
to avoid mold. 
Alum Cochineal. — 
Powdered cochineal. 50 g. 
Alum. 5 g. 
Distilled water. 500 c.c. 
Dissolve the alum in water, add the cochineal, and boil; evapo¬ 
rate down to two-thirds of the original volume, and filter. Add a 
few drops of carbolic acid to prevent mold (Stirling). 
Stain as with alum carmine. It used to be a common practice 
to stain in bulk in alum cochineal and counter-stain on the slide 
with Bismarck brown. 
Iron Aceto-Carmine 1. —For counting chromosomes in pollen 
mother-cells mounted whole, Belling and also Sand used a modified 
aceto-carmine method. The preparations are good for an immediate 
count, but do not last longer than a few days or a week. 
“ Ordinary aceto-carmine is prepared by heating a 45 per cent 
solution of glacial acetic acid to boiling with excess of powdered 
carmine, cooling, and filtering. The young anthers are teased out 
with steel blades or needles in a drop of this until it changes slightly 
toward bluish red. An excess of iron spoils the preparation. 
Iron Aceto-Carmine. — “To a quantity of aceto-carmine a trace 
of solution of ferric hydrate dissolved in 45 per cent acetic acid is 
added until the liquid becomes bluish red, but no visible precipitate 
forms. An equal amount of ordinary aceto-carmine is then added. 
