CHEMICAL MICROSCOPY 



solution (1 g H2PtCl6-()H.,0 in 20 nil water). 

 Keeps well for only about a week to a month 

 at most; can be made up on half the above 

 small scale. 



(B) 1.8 HsPtle in (4 + l)H;iP().. , (250), 

 high Nal. Dissolve 0.5 g Nal in 0.:] ml 

 water, add 2.0 ml H3PO4 and 0.2 ml of 1 :20 

 aqueous platinic chloride solution. Let stand 

 about a day to develop good differentiation 

 from (A). Keeps much better than the pre- 

 ceding, (A); in a few cases a rather old 

 reagent even gives the best results for cer- 

 tain crystals. 



Both of the above are among indispensable 

 reagents for sympathomimetics, central 

 stimulants, and other compounds which are 

 of simple structure or partly acidic, not too 

 easily precipitated. 



(15) HiPth in diluted H2SO4 , (100). 

 H.PtCle soln (1:20 in water) 0.8 ml, (1 -f 3) 

 H2SO4 3.2 ml, Nal 0.46 g. Preferably let 

 stand at least 2 or 3 hours (or overnight) 

 before use. Thereafter it slowly deteriorates, 

 but can be used for a long time. The crystals 

 it gives change to some extent with the age 

 of the reagent. Also, the reagent itself de- 

 posits colored crystals as it partially dries, 

 first around the edge of the cover-glass, 

 where the solution is not covered. Used for 

 ethylamine hydrochloride; uses not much 

 explored. 



(16) H-iPth {acid aqueous). HoPtCle soln 

 (1:20 in water) 4 ml, HCl 1 ml, Nal 1.25 g. 

 If the HCl is omitted, the alkalinity of com- 

 mercial Nal may cause precipitation. Only a 

 little acid would be needed to overcome this, 

 but Amelink indicates generally better re- 

 sults in an acid than in a "neutral" test- 

 drop, anyway. 



Platinic Bromide Reagents 



(17) H.PtBr^ in H.POi , (/ + 3)H,P0i , 

 (^ -f 3)HoS0a , water, HBr, {1 -+- 3)HCl, or 

 (2 + 1) acetic acid, etc. H2PtCl6-6H20 1 g 

 [makes about 1.3 g H^PtBrg]; HBr(40%) 

 2.5 ml, appropriate solvent to make 20 ml 

 (usually). The aqueous reagent (which can 



be made with NaBr instead of HBr) is 

 excellent although strangely neglected in the 

 past. New uses (hanging drop and direct, for 

 sympathomimetics, etc.) especially concern 

 H.PtBrg in (1 + 3)H:iP()4 . The reagent with 

 syrupy H3PO4 develops some precipitation 

 in the bottle, but the clear supernatant solu- 

 tion can be used (rather than adding enough 

 water to prevent precipitation). 



(18) HoPtBrCl^ in cone. HCl. If the above 

 formula is used with concentrated HCl for 

 the solvent, even with twice as much HBr 

 (not exceeding the molecular ratio of 1 HBr 

 to 5 HCl), there is evidence — from micro- 

 crystals — that the precipitating compound 

 is HoPtBrCU . The four other possible Br-Cl 

 combinations form in proportioned mixtures 

 of the strong acids. They can be used by 

 direct addition, for the particular effects; 

 as originally worked out on morphine they 

 were diluted to (60) with the strong acids 

 and some water (up to one-fifth) for best 

 results. Much dilution with water tends to 

 give HoPtBre , regardless of more HCl than 

 HBr being present. 



Platinum and Palladium Chlorides 



(19) HoPtCh in H,POi , (/ + 3)H,P0, , 

 (1 -f 1)H2S0a, water, (1 + 3)HCl, etc. 

 1 g H.PtCle-eH.O in 20 ml of the solvent. 

 The aqueous reagent is of course the tra- 

 ditional one and very valuable. The reagent 

 with (1 + 3)H3P04 is particularly used in 

 the hanging drop for d- and rfZ-amphetamine. 



(20) HoPdCU in H,POi , or water, etc. 

 PdCl2-2H20 1 g; cone. HCl 0.9 ml (in 

 H3PO4) or 0.8 ml (hi water, etc.); H3PO4 , or 

 water, etc. to make 20 ml. Aqueous or 

 partly aqueous reagent may be made wdth 

 NaCl 0.75 g, instead of the HCl (forming 

 NasPdCb). 



Tetraphenvlboron and Reinecke Salt 



(21) Na tctraphcnijlboron, 1 g in 20 ml 

 water (not acidified). Used especially as a 

 hanging drop; remarkable for its sensitivity 



62 



