CHEMICAL MICROSCOPY 



10% HCl), then saturate with Hgl2 (does 

 not take much). Used both for aqueous solu- 

 tions and direct addition to the solid, for 

 heroin, etc. 



(31) Hgh'NaCN and Nal. Dissolve 0.5 

 g good NaCN in 100 ml water and saturate 

 with Hgl2 (use 4J^^ g). (This is a reagent in 

 itself, and more sensitive, but the reagent 

 with excess Nal is recommended more 

 highly for crystals.) Filter the saturated 

 solution and add 8 g Nal per 100 ml. Crys- 

 tals with codeine, etc. 



Cadmium and Lead Iodides. (32) 

 K^Cdh . Cdl2 5 g, KI 4.5 g, water 100 ml. 



(33) Phi 2 in K acetate solution. Dissolve 

 4 g lead acetate (3H2O) and 30 g potassium 

 acetate in water to make 100 ml, and add 

 glacial acetic acid drop wise just to faint 

 acidity to methyl red (reacts brown instead 

 of yellow); then add 4.5 g KI. 



Many crystals with both the above. 



Mercuric Chloride Reagents. (34a) 

 Simple HgCl2 (5%) is commonly used but 

 usually added to solutions containing dilute 

 HCl, or the hydrochloride of the base, so 

 that actually more or less of the following 

 chloro-acid is present. 



(b) HHgCls . HgCla 5 g, coned HCl 1 ml, 

 water 99 ml. 



(c) NaHgCls . HgCl2 5 g, NaCl 0.75 g, 

 water 100 ml. 



(d) HgCl2 & HCl. HgCl2 5 g, cone. HCl 

 15 ml, H2O 85 ml. This is less sensitive; 

 useful especially for quinine. 



Ferric Chloride Reagents. (35a) FeCls 

 in HCl; HsFeCle . FeCU-GHzO 10 g, cone. 

 HCl 100 ml. For addition to aqueous solu- 

 tions (cocaine, methadone, etc.). 



(b) HsFeCle for direct addition to solids: 

 FeCl3-6H20 10 g, coned HCl 17.5 ml, water 

 to make 100 ml. 



Organic Reagents. (36) Picric acid is 

 outstanding. 



(a) A saturated aqueous solution (about 

 1K%). Many crystals, (b) A 0.2% aqueous 

 solution. Picric acid crystals (10%) water) 

 0.2 g, water 100 ml. Cinchonine is an example 

 of a base yielding crystals far more readily 



with this dilute reagent than with the satu- 

 rated. This weak solution may also be used 

 for direct additions. 



(c) Half-saturated Sodium Picrate. Pre- 

 cipitate sodium picrate from saturated picric 

 acid solution with concentrated sodium 

 acetate. Filter, then prepare a saturated 

 solution of sodium picrate. Filter this from 

 excess crystals and dilute with an equal vol- 

 ume of water. Crystals with bases are often 

 obtained more readily than with the satu- 

 rated acid. 



(37) Other nitro-organic reagents. Styphnic 

 acid (trinitroresorcin) and Trinitrobenzoic 

 acid are used in saturated solutions. 



Simple Oxygen Acids. (38) CrOz and 

 HCrOzCl. 



(a) 5 % CrOs . The chloroacid or its salt 

 (following formulas) is more sensitive and 

 better. 



(b) HCrOsCl. Stock solution of 20 g CrOa 

 in water to make 100 ml (this may be used 

 as a concentrated CrOs reagent in itself). 

 Reagent: 1 ml of foregoing stock solution 

 plus 2 ml water and 1 ml coned HCl. Will 

 keep for some time; slowly darkens. 



(c) NaCrOsCl. Add 1 g NaCl to 4 ml of 

 the 5 % CrOs . Keeps well. 



(39) Perchloric acid. 5 % solution of HCIO4 

 or NaC104 . 



(40) Permanganic acid oxidizes most alka- 

 loids and other bases, but the stable crystal- 

 line permanganates are quite distinctive. 

 Unfortunately reducing impurities can easily 

 spoil a test. 



(a) KMn04 2 g in 100 ml water, with a 

 few drops of syrupy H3PO4 . 



(b) HMn04 in dilute H2SO4 , for direct 

 addition. Use a stock solution of 1 % KMn04 . 

 Reagent: 2 ml stock solution, 1 ml (1 -f 3) 

 H2SO4 . Make up fresh for use. Used for 

 cocaine, meperidine, methadone, etc. 



Basic Reagents 



Precipitation of the free base by addition 

 of the reagent to a neutral or slightly acid 

 solution of the salt of an alkaloid, etc. 



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