90 CARMINE STAINS. 



absolute or of any weaker grade), 1 or 2 drops of HC1 and 

 an excess of carmine, and boil until you get a clear solution, 

 taking care that there remain an excess of carmine. This 

 ought to give a nuclear stain, without the aid of HC1 for 

 washing out. 



BRASS (Zeit.f. iviss. Mik., ii, 1885, p. 303) takes 100 c.c. of 

 70 per cent, alcohol, 15 drops of HC1, and an excess of carmine. 

 An old formula of PAUL MAYER'S (M. T. Zool. Stat. Neapel, iv, 

 1883, p. 521; Journ. Eoy. Mic. Soc. (N.S.), iv, 1884, p. 317), 

 which gives a more powerful stain than the preceding, is as 

 follows : 



Four gr. carmine are dissolved in 100 c.c. of 80 per cent, 

 alcohol with the addition of 30 drops of concentrated pure 

 hydrochloric acid, and heated for about half an hour in the 

 water-bath ; the solution is filtered whilst still hot, and the. 

 superfluous acid is carefully removed by the addition of caustic 

 ammonia, added until the carmine begins to be deposited. 

 This solution stains very rapidly (embryos of lobsters are 

 stained in about a minute) and intensely, though diffusely ; 

 the preparations must be washed out with HC1 alcohol if a 

 nuclear stain is required. 



- The heating of alcohol of so high a grade as 80 per cent, 

 being troublesome, not to say dangerous, the process may be 

 modified by dissolving the carmine in 15 c.c. of water acidu- 

 lated with the HC1, adding 95 c.c. of 85 per cent, alcohol, and 

 then neutralising with ammonia. 



If it be desired to dilute any of these solutions it should be 

 done with alcohol, not water, and alcohol should be taken for 

 washing out. 



165. Alcoholic Boric Acid Carmine (FEANCOTTE, Bull. Soc. Beige 

 Mic., 1886, p. 48). Carmine 0'4 gr. ; boric acid, 5 gr. ; water, 25 c.c. ; 90 

 per cent, alcohol, 75 c.c. Boil and filter. 



166. Dutilleul's Picro-borax Carmine (Bull. Sci. Dep. Nord, xvi, 

 1885, p. 371). This is quoted here as having the distinction of being the 

 very worst stain I have ever tried. 



