CHAPTER XII. 141 



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 neutral- 

 ise the ammonia, which it only does imperfectly. See MAYER in 

 Zeit. wiss. Mik., xiv, 1897, p. 18. 



229. RANVIER'S Piero-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 nitration the precipitate that 

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

 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. 



Overstains 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-carmine, 

 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 cent, 

 of chloral hydrate. Gives an almost neutral preparation. 



231. MAYER'S Picro-Magnesia Carmine (Zeit. wiss. Mik., xiv, 1897, 

 p. 25) is relatively constant and innocuous to tissues. It consists of 

 1 vol. of the stock solution of magnesia-carmine ( 227), and 10 vols. of 

 a 0-6 per cent, solution of picrate of magnesia, or of equal parts of the 

 weak solution and the picrate solution. The picrate may be obtained 

 from GRUBLER & HOLLBORN, or the solution may be made by heating 

 0-25 grm. of carbonate of magnesia in 200 c.c. of 0-5 per cent, solution 

 of picric acid, allowing to settle, and filtering. 



DE GROOT'S picro -magnesia carmine (ibid., xxix, 1912, p. 184) contains 

 ammonia, which is bad, and seems to me superfluous. 



232. Other Formulae for Piero-Carmine and Other Aqueous Carmines 

 (Acid and Alkaline). I have tried most of them, and found no real 

 advantage in any of them (see previous editions). 



B. ALCOHOLIC CARMINE STAINS. 



233. Alcoholic Borax-Carmine (G-RENACHER, Arch. mik. Anat.. 

 xvi, 1879, pp. 466 et seq.). Make a concentrated solution of carmine in 

 borax solution (2 to 3 per cent, carmine to 4 per cent, borax) by 

 boiling for half an hour or more (or allowing it to stand, with 

 occasional stirring, for two or three days) ; dilute it with about an 



