1880.] 



MICROSCOPICAL JOURlSrAL. 



23 



oven, allowed to cool, then well fil- 

 tered and the filtrate evaporated 

 to dryness. When wanted for use 

 the dry powder is dissolved in water, 

 in the proportion of one part by 

 weight of picro-carmine, to one 

 hundred parts by weight of water. 



It is very difficult to decide when 

 the mixture of carmine and picric 

 acid solutions becomes saturated, 

 and the simple watery solution soon 

 hecomes mouldy. 



Some experiments were made in 

 the anatomical laboratory of the 

 Cornell University to determine 

 definitely, if possible, the process of 

 making a solution that would keep 

 for any length of time. 



1. It was found that equal parts 

 by weight of picric acid and carmine 

 gave the best results. ^ 



2. The picric acid should be 

 dissolved in one-hundred times its 

 weight of water, using heat if 

 necessary. 



3. The carmine should be dis- 

 solved in fifty times its weight of 

 strong ammonia. 



4. Mix the two solutions. It 

 seems to make no difference in the 

 result which solution is poured into 

 the other. 



5. Use porcelain evaporators and 

 glass funnels. 



The best results were obtained 

 when the solutions were made at 

 the ordinary temperature of the 

 laboratory, 17° C, and then eva- 

 porated tliree-fourths at a tempera- 

 ture of 40°-45°C. The solution 

 should be allowed to cool, and 

 filtered through two thicknesses 

 of filter paper. The filtered liquid 

 is then evaporated to dryness at 

 40 ° C. or at the ordinary tempera- 

 ture. 



*One gramme each of picric acid and 

 carmine will make enough picro-carmine to 

 last an individual or a small laboratory a long 

 time. The best carmine, that known as No. 

 40, should be used. 



If the preparation has been 

 successful the residue dissolved in 

 one-hundred times its weight of 

 water should give a clear solution, 

 after filtering. Make 50'^-'=- of such 

 a solution and filter it through two 

 thicknesses of filter paper and a 

 fine cotton filter moistened well and 

 crowded into the neck of the 

 funnel. Filter the solution four or 

 five times through the same filter, 

 and a clear solution will probably 

 be obtained. In case a clear solution 

 cannot be obtained by repeated 

 filtering, the whole of the powder 

 may be dissolved in the i3ro]3ortion 

 given above and allowed to stand 

 a few days in a tall, narrow vessel. If 

 the finely suspended particles settle, 

 the top will be clear and may be 

 decanted ; but if the fluid remains 

 cloudy, a quantity of ammonia 

 equal to that originally used should 

 be added to it, and the evaporation 

 of three-fourths should be re- 

 peated with the subsequent filtra- 

 tion and evaporation to dryness. 

 Usually, however, if the method 

 given above be followed, one will 

 succeed the first time. In case the 

 third evaporation should not give 

 a clear solution, it is advisable to 

 begin again with new materials. 



When a clear solution is obtained 

 there should be added to every 

 lOO'^'^- of the picro-carmine 25'^-'=- 

 of strong glycerine and lO^^-^- of 

 95 per cent, alcohol ; there Avill thus 

 be formed a permanent solution, 

 that may be kept perfectly clear by 

 filtering once in five or six months. 



The characteristics of this stain- 

 ing fluid are very clearly set forth 

 by Ranvier as follows : 



1. The staining is double, — some 

 parts staining red and others yellow. 



2. The carmine is entirely neu- 

 tral. 



. 3. If desirable, the yellow color 

 may be removed by soaking in 

 water. 



