CAKMIM: .VND COCHINEAL STAINS. 147 



226a. ORTH'S Lithium-Carmine (see early editions) macerates 

 strongly, and is superfluous. For that of BEST, see Zeit. iviss. Mile., 

 xxiii, 190t>, p. 322. 



227. Magnesia-Carmine (MAYER, Zeit. wiss. Mik., xiv, 1897, p. 23). 

 Take 1 grm. carmine, O'l grin, magnesia usta, and 50 c.c. distilled 

 water, boil for five minutes, filter, and add three drops of formol. This 

 is the stock solution. A weak solution may be made by boiling O'l grm. 

 carmine for half an hour in 50 c.c. of magnesia water (made by leaving 

 O'l grm. of magnesia usta in contact with 100 c.c. of spring water for a 

 week with frequent agitation, and decanting when required for use). 

 Said to be less injurious to tissues than the other alkaline carmines. 



228. As to Picro -carmine. The term " picro-carmine " is 

 commonly used to denote a whole tribe of solutions in which 

 carmine, ammonia, and picric acid exist uncomlined in hap- 

 hazard proportions. These solutions do not contain a double 

 salt of picric and carminic acid and ammonia,, or picro-car- 

 min ate of ammonia. They are always alkaline, and frequently 

 injurious to tissues. The raison d'etre of picro-carmine does 

 not lie in its capacity of affording a double stain, but in that 

 the picric acid in it is supposed to neutralise the ammonia, 

 which it only does imperfectly. See MAYER in Ztit. wiss. 

 Mik., xiv, 1897, p. 18. 



229. RANVIER'S Picro-carmine, Original Formula (Traite, p. 100). 

 To a saturated solution of picric acid add carmine (dissolved in. 

 ammonia) to saturation. Evaporate down to one fifth the original 

 volume in a drying oven, and separate by filtration the precipitate that 

 forms in the liquid when cool. Evaporate the mother liquid to dryiiess, 

 and you will obtain the picro-carmine 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. 



For slow staining, dilute solutions may advantageously have 1 or 2 

 per cent, of chloral hydrate added to them. 



Overstaiiis may be washed out with hydrochloric acid, say 0'5 per cent, 

 in water, alcohol, or glycerin. 



Preparations should be mounted in balsam, or if in glycerin, this 

 should be acidulated with 1 per cent, of acetic acid, or better, formic 

 acid. 



RANVIER'S Newer Formula does not give a more constant product 

 (see previous editions). 



230. VAN WIJHE dissolves 0'5 per cent, of the dry ammonia-carmiiie j 

 225, in a 1 per cent, solution of neutral picrate of ammonia, boils until 

 the vapour ceases to blue reddened litmus paper, and adds 1 per c nt, 

 of chloral hydrate. Gives an almost neutral preparation. 



