CARMINE AND COCHINEAL 141 



INIayer {ibid., xiv, 1897, p. 29) makes a stronger stain by taking 

 2 grm. carmine, 5 grm. alum, and 100 c.c. water, and boiling for an 

 hour. 



252. Acetic Acid Alum-Carmine (Henneguy, in Troite des Mcth. 

 Tcchn., Lee et Henneguy, 1887, p. 88). Excess of carmine is boiled 

 in saturated solution of potash alum. After cooling add 10 per cent, 

 of glacial acetic acid, and leave to settle for some days, then filter. 



For staining, enough of the solution is added to distilled water to give 

 it a deep rose tint. In order to ensure rapid diffusion it is well to bring 

 the tissues into the stain direct from 90 per cent, alcohol. Stain for 

 twenty-four to forty-eight hours, and wash for an hour or two in 

 distilled water. Mount in balsam. You can mount in glycerin, but 

 the preparations do not keep so well. 



The advantage of this carmine is that it has much greater power of 

 penetration than the non-acidified alum-carmine. 



253. Cochineal Alum-Carmine (Partsch, Arch. mik. Anat., xiv, 1877, 

 p. 180). Powdered cochineal is boiled for some time in a 5 per cent, 

 solution of alum, the decoction filtered, and a little salicylic acid added 

 to preserve it from mould. 



Another method of preparation has been given by Czokor (ibid., 

 xviii, 1880, p. 413). Mayer finds that Partsch's is the more rational, 

 the proportion of alum in it being exactly right, whilst in Czokor's it 

 is insufficient. Partsch's fluid also keeps better, 



Rabl {Zeit. wiss. Mik., xi, 2, 1894, p. 168) takes 25 grm. each of 

 cochineal and alum, 800 c.c. of water, and boils down to 600 c.c. He 

 prefers this because it is not so purely nuclear a stain as the others. 



These solutions give a stain that is practically identical with that 

 of alum-carmine made from carmine, with perhaps even more delicate 

 differentiations . 



Rawitz {Zeit. iviss. Mik., xxv, 1909, p. 392) takes cochineal 4 grm., 

 nitrate of aluminium (or ammonio-sulphate of cobalt) 4 grm., water 

 100 c.c. and glycerin 100 c.c. Only for sections. 



254. Mayer's Carmalum {Mitth. Zool. Stat. Neapel, x, 1892, 

 p. 489). Carminic acid, 1 grm. ; alum, 10 grm. ; distilled water, 

 200 c.c. Dissolve with heat (if necessary). Decant or filter. 

 Add some antiseptic, either 1 c.c. formol, or 0-1 per cent, salicylic 

 acid, or 0-5 per cent, salicylate of soda. The solution will then 

 keep. It stains well in bulk, even osmium objects. If washed 

 out with distilled water only, the plasma will remain somewhat 

 stained. If this be not desired, wash out carefully with alum 

 solution, or, in difficult cases with weak acid, followed in either 

 case with water. The general effect is that of an alum-carmine 

 stain. 



A weaker solution may be made by taking from three to five 

 times as much alum and five times as much water, and dissolving 

 in the cold. 



With either solution the objects to be stained should not have an 

 alkaline reaction. 



Rawitz's Carmalum {Anat. Anz., xv, 1899, p. 438). Ammonium 

 alum, 20 grm. ; distilled water, 150 c.c. ; glycerine, 150 c.c. ; 

 carminic acid, 2 grm. The ammonium alum should first be 

 dissolved in the distilled water, then the carminic acid added, 



