REAGENTS FOR MICROCRYSTAL IDENTIFICATIONS 



Chloraiiric Acid (Gold Chloride) Rea- 

 gents 



(12) HAuCh in H^PO, , (1 + 2)HzP0i , 

 (1 + l)H2S0i , water, cone. HCl, (1 + 3)HCl, 

 or {2 -{- 1) acetic acid, etc. 1 g HAuCU -31120 

 in 20 ml (usually) of the appropriate sol- 

 vent; further dilution (60) with H3PO4 , 

 (1 + 1)H2S04 , coned HCl, or (2 + 1) acetic 

 acid may be used for tests of direct addi- 

 tion with easily precipitated compounds. 

 In the traditional procedure, that is, simply 

 in water and applied to aqueous solu- 

 tions, HAuCU is probably the best single 

 reagent known for alkaloid-type compounds. 

 HAuCU in (1 -^ 2)H3P04 is especially used 

 in hanging drop tests for volatile bases and 

 in direct addition to solids (salts of simple 

 bases, etc.) — as well as for addition to aque- 

 ous solutions. No cover-glass is used and 

 water is then allowed to evaporate from the 

 test-drop if necessary for precipitation and 

 crystallization. 



Bismuth and Platinum Iodide Reagents 



HsBile and H2Ptl6 are very general precipi- 

 tants, so much so that they are the two pre- 

 cipitating agents most com.monly used — 

 though only in aqueous solution — for devel- 

 oping spots of alkaloid-type compounds in 

 paper chromatography. (At this time the 

 writer does not yet know of any paper-chro- 

 matographer who has used phosphoric acid, 

 or even diluted sulfuric, to increase the gen- 

 erality and sensitivity of these reagents.) 



Bismuth Iodide Reagents 



An aqueous (strongly acid) HsBile reagent 

 is a traditional one from the last century; 

 but as commonly made, it soon decomposes 

 in part; then some effects are still due to 

 the HsBile , but others to iodine-KI. Some 

 users age their reagent for a time to obtain 

 consistent results. Amelink even added io- 

 dine crystals to have a mixed reagent from 

 the start. The reagents given here, however, 

 depend upon HsBile alone. 



For crystal purposes, phosphoric acid has 

 been difficult to use because colored crystals 

 are likely to form due to the reagent itself. 

 The use of Bils and HI to make up the rea- 

 gent has not as yet solved any important 

 problems either, so the formulas given here 

 simply employ a concentrated bismuth 

 nitrate solution. The reagents have a bright 

 orange color and are to be remade when they 

 darken appreciably. This occurs very soon 

 with (1 -f 7)H2S04 , and too rapidly for 

 convenience even with aqueous reagent, if 

 no preservative is used. Sodium hypophos- 

 phite is here introduced as a preservative, 

 which makes the reagents comparatively 

 long-lasting. 



Cone. Bi(N03)3 soln: Dissolve 50 g bis- 

 muth subnitrate in 70 ml (1 -f 1)HX03 and 

 dilute to 100 ml with w^ater. 



(13) H^Bile in {1 + 7)H2SOi or in water, 

 etc. 



(a) HgBile in (1 -f 7)H2S04 . KI 1.25 g, 

 H2O 2.0 ml, (1 + 3)H2S04 2.5 ml, cone. 

 Bi(N03)3 soln 0.5 ml, Na hypophosphite 

 0.05 g. Mix. Used especially for hanging- 

 drop tests and direct-addition tests for sym- 

 pathomimetics, etc. 



(b) HsBile (aqueous). Omit the diluted 

 H2SO4 , using simply 4.5 ml water. Used 

 direct for theophylline and related com- 

 pounds; also for addition to aqueous solu- 

 tions (traditional). (0.04 g hypophosphite is 

 enough.) 



(c) Double strength HsBile (aqueous) 

 may sometimes be preferred. KI 2.25 g, Na 

 hypophosphite 0.05 g, HoO 4.0 ml, cone. 

 Bi(N03)3 soln 1 ml. Mix. 



Platinic Iodide Reagents 



1 g H2PtCl6-6H20, with iodide, makes 

 about 1.8 g H2Ptl6 . 



(14) HiPth with H^POa , (A and B). 

 Formulas for small dropping bottles. 



(A) 1.8 IloPtle in (2H + 1)H3P04 , (250), 

 with minimum Nal. Dissolve 0.04 g Nal in 

 0.5 ml H2O; mix with 1.8 ml H3PO4 , and 

 add 0.2 ml of 1:20 aqueous platinic chloride 



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