OTHER FORMULAE FOR AMMONIA PIORO-CARMINE. 83 



Put them into a stoppered bottle and leave them for two or 

 three months in a warm place. Then put them into a large 

 crystallising dish and let them putrefy. When the liquid has 

 become reduced by evaporation to four fifths of its original 

 volume, remove the crystals that have formed at the bottom, 

 dry them, and dissolve them in a little warm water. Filter 

 the solution, and examine it with the microscope to see 

 whether the carmine is really dissolved. If not, add water 

 and ammonia, and let the solution putrefy again; evaporate 

 and examine as before. When you have got your carmine 

 combined, evaporate the solution to dryness in a stove, and 

 reduce the picro-carminate to powder. 



For staining, dissolve 1 gramme of the powder in 100 

 grammes of water, and add a crystal of thymol to prevent 

 the development of mould. 



Ranvier's Original Formula (Traite, p. 100) was as follows : To a 

 saturated solution of picric acid add carmine (dissolved in ammonia) to satu- 

 ration. Evaporate down to one fifth the original volume in a drying oven ; 

 and separate by filtration the precipitate, poor in carmine, that forms in the 

 liquid when cool. Evaporate the mother liquor to dryness, and you will 

 obtain the picro-carminate in the form of a crystalline powder of the colour 

 of red ochre. It ought to dissolve completely in distilled water ; a 1 per 

 cent, solution is best for use. 



146. Picro-Carmine (Weigert's formula, Virchow's ArcMv, 

 Bd. 84, pp. 275, 315 ; Zool. Jahr., 1881, p. 40). Two grammes 

 of carmine are soaked for twenty-four hours (in a vessel pro- 

 tected from evaporation) in 4 grammes of ammonia; 200 

 grammes of concentrated solution of picric acid are then 

 added, and the whole put away for twenty-four hours more. 

 Small quantities of acetic acid are then added " until the first 

 slight precipitate appears even after stirring." The whole is 

 again put away for twenty-four hours more, when it will be 

 found that there has formed a precipitate that can only par- 

 tially be removed by filtration ; ammonia is then added drop 

 by drop at intervals of twenty-four hours, until the solution 

 becomes clear. If the solution stains too yellow, acetic acid 

 is added ; if it overstains red, a little ammonia is again added. 

 All badly staining samples of picro-carmine may be improved 

 in the same way by addition of acetic acid or ammonia. 



147. Other Formula for Ammonia Picro-Carmine. GAGE, Am, 

 M. Mic. Journ., i, 1880, p. 22 ; Joum. Roy. Mic. Soc., vol. iii, p. 501 



