ACETIC ACID ALUM-CARMINE. 85 



378) add a small percentage of sulphate of sodium, with 

 object of enhancing the energy of the stain. It should not be 

 forgotten that sodium sulphate is a substance that exercises a 

 very peculiar action on nuclei (see PFITZNEE, Morph. Jahrb., 

 xi, 1, 1885). 



It has already been sufficiently repeated that alum-carmine 

 is one of the best stains to be found outside the coal-tar 

 colours. It is particularly to be recommended to the beginner, 

 as it is easy to work with ; it is hardly possible to overstain 

 with it (except muscle). 



150. Alum-Carmine with Osmic Acid (ZOLTAN VON KOBOZ, in 

 litt.). To 50 or 60 grms. of water is added alum-carmine 

 until the mixture is of an almost red rose colour ; about ten 

 drops of a -njVo solution of osmic acid are then added. (The 

 mixture should have an appreciable smell of osmic acid.) The 

 objects to be stained remain in the mixture for about thirty- 

 six hours in the dark. It is hardly necessary to wash them, 

 as the stain is perfectly precise without that. It is important 

 to perform the staining in a well-closed vessel, in order to pre- 

 vent the evaporation of the osmium. 



I have used this stain with the most diverse objects, and can 

 most highly recommend it. The result is a sharp nuclear 

 double stain (resting chromatin and nucleoli purple, kinetic 

 chromatin red, the rest brown) . Very valuable for staining 

 soft tissues in the mass. 



151. Acetic Acid Alum-Carmine (HENNEGUY, Traite des Meth. 

 Techn., LEE et HENNEGUY, 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. The deposit of carmine and alum that forms during 

 that time is removed by filtration. 



For staining, enough of the solution is added to distilled 

 water to give it a deep rose tint. Stain for twenty -four to 

 forty-eight hours, and wash for an hour or two in distilled 

 water. (It is important that the water should be distilled in 

 order to avoid the formation of crystals.) Dehydrate with 

 alcohol and 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 great power of 



