610 Journal of Applied Microscopy. 



nucleic acid with aluminum from the alum, and haemalum from the aluminum 

 salt of haematein. 



Hiematein with Aluminimi. — This gives pure nuclear stains only when alum is 

 relatively abundant, or when aluminum chloride is in excess in an alcoholic 

 soluble chloride (CaClg preferably). The presence of free acid or alum is 

 desirable for mucin, or, better, a mixture containing relatively much haematein 

 diluted with potassium acetate, spring water, etc. 



ALUM-HiEMATOXYLiN. — Of the many preparations of this form of stain the 

 ■ best are : Delqfield's, which is formed of a saturated solution of ammonium alum 

 (lOOcc), with a solution of one gr. of haematoxylin in six cc. of strong alcohol. 

 This mixture is allowed to stand three to four days in an open flask, and 25 cc. 

 of glycerine and methyl alcohol are added, and the whole allowed to stand at least 

 two months in the open until it is dark colored. Erliclis mixture is composed of 

 one gr. haematoxylin, fifty cc. of absolute alcohol, five cc. of acetic acid, fifty cc. of 

 glycerine, and water and alum in excess. This is allowed to become dark red in 

 an open flask, and if well corked keeps for a year or more. Sections stain very 

 rapidly, and masses should be stained through but not over-stained ; sharp 

 nuclear stains result, owing to the acid present in the older mixtures. 



Several other haematoxylin mixtures are taken up that must be passed over, 

 and these stains left with this incomplete review. The group of cochineal stains 

 is next considered. 



Cochineals are obtained from the female cochineal insect Coccus cacti, by 

 grinding and extraction. 



Alum Cochineal. — Into a five per cent, solution of alum is put finely ground 

 cochineal. This is boiled, filtered, and some salicylic acid added for keeping it. 

 Another process (Crooker's), is to take cochineal alum (7 g.), and water (700 cc). 

 This is reduced to 400 cc. by boiling. 



A New Cochineal Tificture. — (Mayer.) This is made of cochineal 10 gr., 

 calcium chloride 10 gr., aluminum chloride i gr., nitric acid 16 drops, alcohol 

 (50 per cent.) 200 cc. The finely pulverized cochineal and salts are mixed with 

 the alcohol, and acid added, and the whole heated to boiling point ; this is allowed 

 to stand cold, but well shaken for a few days, then filtered. 



Carmine. — This is a combination of carminic acid with aluminum and cal- 

 cium, and a not well known albuminous substance, which is obtained from 

 cochineal. It is easily soluble in caustic alkalies, carbonates, borax, and 

 acidulated alcohols. 



Acid Aqueous Mixtures. — Alum-carmine (Grenacher). An aqueous solution of 

 one to five per cent, potassium or ammonium alum is boiled for ten to twenty min- 

 utes with one-half to one per cent, carmine, and filtered after cooling. This is 

 however, a stain of poor penetration, but does not over-stain. Acetic acid car- 

 mine is made by boiling a forty-five per cent, solution of acetic acid till satur- 

 ated with carmine. This is used as a stain for living objects, and gives a sharp, 

 nuclear stain, but is not permanent. Formic acid carmine is also used, and one 

 author puts his objects stained in acetic acid carmine into a one per cent, 

 solution of iron oxide-ammonium-citrate, forming as a stain iron carminate. 



Basic and So-called Neutral Aqueous Mixtures. — Magnesium, lithium, 



