CARMINE AND COCHINEAL STAINS. 169 



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 has also 

 the advantage of keeping better. 



RABL (Zeit. f. wiss. Mik., xi, 2, 1894, p. 168) takes 25 grms. each of 

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



These solutions are to all intents and purposes " alum- 

 carmines." They give a stain that is practically identical 

 with that of alum- carmine made from carmine, with perhaps 

 even more delicate differentiations (but that depends so much 

 on the quality of the carmine, the quality of the cochineal, 

 and the nature of the objects to be stained, that no absolute 

 rule can be stated). They should be used in exactly the 

 same way as the carmine fluid. 



215. Acetic Acid Alum- Carmine (HENNEGUY, in Traite des 

 M'-th. techn., LEE et HENNEGUY, 1887, p. 88). Excess of car- 

 mine 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 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 as in balsam. 



The advantage of this carmine is that it has greater power 

 of penetration than the non-acidified alum-carmine, and stains 

 deep-seated layers of tissue just as well as the superficial 

 ones. The colour of the stain is a somewhat inelegant violet, 

 but this can be changed to a warmer tone by treating the 

 objects with dilute HC1, as for borax-carmine objects. 



216. Alum-Carmine and Picric Acid. Alum-carmine objects 

 may be double-stained with picric acid. LEGAL (Morph. 

 Jahrb.. viii, p. 353) combines the two stains by mixing ten 

 vols. of alum-carmine with one of saturated picric acid solu- 

 tion. I consider this to be a very recommendable practice. 



217. Aceto-Carmine (Acetic Acid Carmine) SCHNEIDEE'S formula, 

 Zool. Anzeig., No. 56, 1880, p. 254). To boiling acetic acid of 45 per cent. 



