1892.] THE MICROSCOPE. 153 



Pici'o Car7?zine. — I. Carmine, i grm. ; liquor ammonise, 4 

 c.c. ; mix and add 5 grms. picric acid. II. Carmine, 15 grms. ; 

 picric acid, concentrated solution. Agitate the mixture (I) from 

 time to time for 2 days ; let it settle ; decant and evaporate de- 

 canted liquid at ordinary temperature ; redissolve the dry residue 

 in water, making \% or 2% solution ; filter when necessary. 

 II. Triturate the carmine in a mortar until very fine ; add enough 

 ammonia to dissolve the carmine : to this add slowly-concentrated 

 solution of picric acid until the mixture has a blood-red color ; 

 keep in a shallow dish until all odor of ammonia has disappeared ; 

 filter ; keep in a well-stoppered bottle ; add a few drops of car- 

 bolic acid ; filter before using. 



Picro Carinine and Eosin. — Solution of picric carmine, 1%", 

 I part ; watery solution of eosin, 2%, i part. For small organ- 

 isms \ to 4 days ; wash in 70%, then in 90% alcohol. 



METAI.LIC STAINS. 



Arnitioniacal Nitrate of Silver. — Silver nitrate 0.7^ to o.^ 

 per cent, with ammonia. Add to nitrate of silver solution enough 

 ammonia to re-dissolve the precipitate which forms at first ; dilute 

 to 0.75 per cent, or 0.5 per cent. 



Gold Chloride. — A. Gold chloride, i grm. ; water, 3,000 c.c. ; 

 hydrochloric acid, 30 drops. B. Alcohol, i part; formic acid, 

 I part. Sections treated with yl, then transferred to ^, where 

 reduction of the gold takes place. 



Potassi?i??i Gold Chloride. — A. Potas. gold chloride, i part; 

 water, 10,000 parts ; hydrochloric acid, a trace. P. Water, 2 to 

 3,000 parts ; hydrochloric acid, 1 part. C. Alcohol, 60 percent., 

 1,000 parts; hydrochloric acid, i part. Sections hardened in 

 ammonium bichromate are put in A for from 10 to 12 hours, 

 until they are of a light violet color, washed in B. and transferred 

 to C. 



Osmic Acid and Silver Nitrate. — A. Potas. bichromate, 2 

 per cent., 10 parts; osmic acid, i per cent., i part. B. Silver 

 nitrate, i part; water, 200 parts. Objects soaked in A for sev- 

 eral hours, transferred to B for at least 8 hours. 



Silver Nitrate. — A. Silver nitrate, 0.25 to 0.5 parts; water, 

 100 parts. B. Salt, 0.75 parts ; water, 100 parts. Sections 20 

 to 40 seconds in ^, then in B\ move them about in both, then 

 expose to the light. 



Silver Nitrate and Silver Iodide. — A. Silver nitrate, i part; 

 water, 100 parts. B. Silver iodide, i part; water, 100 parts ; 

 potassium iodide, a trace. C. Silver nitrate, o.i part; water, 

 100 parts. Put the sections in A (in the dark) ; after 2 or 3 min- 

 utes add a few drops of B ; wash the sections in water and expose 

 for 2 days in C to the action of the light (cornea). 



