148 CHAPTER XII. 



231. MAYER'S Picro-magnesia Carmine (Zeit. wiss. Mile., 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 

 O25 grms. 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 Picro-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 (GRENACHER, Arch. mik. Anat., 

 xvi, 1879, p. 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 equal volume of 70 per cent, alcohol, 

 allow it to stand some time and filter. 



Preparations should remain in the stain until they are 

 thoroughly penetrated (for days if necessary), and then 

 be brought (without first washing out) into alcohol of 70 per 

 cent, acidulated with 4 to 6 drops of hydrochloric acid to each 

 100 c.c. of alcohol. They are left in this until they havo 

 taken on a bright transparent look (which may require days), 

 and may then.be washed or hardened in neutral alcohol. 

 Four drops of HCL is generally enough. Three drops I find 

 not quite sufficient. 



For delicate objects, and for very impermeable objects, it 

 may be well to increase the proportion of alcohol in the stain ; 

 it may conveniently be raised to about 50 per cent. It should 

 not exceed 60 per cent, in any case (MAYEK). 



This stain used to be the most popular of any for staining 

 in bulk. It is easy to use, and gives a most splendid colora- 

 tion. But it is not so penetrating as is commonly supposed, 

 and lias the defect of sometimes forming precipitates in the 

 cavities of bulky objects which cannot be removed by washing 

 out. And the fluid is alkaline, and therefore may not be 

 suitable for certain delicate work. 



