SYMPATHOAll.METICS AND CENTRAL STIMULANTS 



(41a) 5% NaOH. Sometimes a concen- 

 trated solution is used. 



(b) 5 % Na3P04 . The alkalinity is about 

 the same as for 5% Na2C03 , -which is more 

 often used, but effervesces when added to an 

 acid solution. 



(c) 5% K2Cr04 . Precipitation of a 

 chromate of a strong base is possible, but the 

 principal use and value is as a basic group 

 reagent for the weak alkaloids that are quite 

 insoluble in water. It must, of course, be 

 added to solutions that are only slightly acid, 

 or, if strongly acid, the effect is that of 

 K2Cr207 (similar to CrOs). 



(d) Concentrated K acetate, 30 g in water 

 to make 100 ml. For precipitation and 

 crystals with very weak insoluble bases. 



Cyanides 



(42) Gold Cyanide Reagent. Dissolve 1 g 

 HAuCU-SHaO crystals in 20 ml water. Add 

 0.5 g NaCN a little at a time; if there is im- 

 mediate precipitation add just enough NaCN 

 to redissolve; otherwise 0.5 g should be the 

 right amount. Makes a colorless solution, 

 which sould not turn red litmus blue (if it 

 does, acidif}^ with acetic acid). 



(43) Platinum Cyanide Reagent. Dissolve 

 1 g H2PtCl6-6H20 m 18 ml water and add 

 1.5 g NaCN. Solution may warm up and be- 

 come rather brown; if not, warm a little on 

 the water bath until it just begins to darken, 

 then cool. Cautiously acidify with 2 ml (1 -t- 

 3) H2SO4 . There is usually a small amount 

 of brown precipitate, apparently due to the 

 reaction going a little too far, in part ; this is 

 removed by filtering either before or after 

 acidifying. The solution is brown but not a 

 dark brown. 



(44) HiFeiCN)^ with H^POi . A stock so- 

 lution is kept of 10 g K4Fe(CN)6-3H20 in 

 water to make 100 ml. Reagent: Mix 3.5 ml 

 of the stock solution with 0.25 ml syrupy 

 H3PO4 . Has to be made fresh as it will not 

 keep. 



Simple Halides and Pseudohalides. 



(45) 5 % solutions of KI, NaSCN, NaNOz . 

 They are also used in concentrated solutions. 



Charles C. Fulton 



SYMPATHOMIMETICS AND CENTRAL 

 STIMULANTS 



Most of these are relatively simple com- 

 pounds, compared with alkaloids (q.v.), and 

 are not so readily precipitated. Some which 

 have alcoholic and phenolic hydroxyl groups 

 are not precipitated at all by the usual 

 aqueous reagents, which are described in the 

 article "Alkaloids and Alkaloidal-type Pre- 

 cipitation". The following 14 tests are se 

 lected for tabulation in Table 1. Five rea- 

 gents are applied directly to a very little of 

 the solid, with addition of a cover-glass : 



(1) 1.3 HAuBr4 in H3PO4 , (20) 



(2) 1.3 HAuBr4 in 2H3P04-1(2 + 3)- 

 H2SO4 , (90) 



(3) 1.8 H2Ptl6 in (2H + 1)H3P04 , (250), 

 with minimum Nal 



(4) 1.8 H2Ptl6 in (4 -f 1)H3P04 , (250), 

 high Nal 



(5) Iodine-HI-H3P04 reagent. 



Three reagents, which contain more water 

 than the five above, are used in two tests 

 each. They are applied to the solid without 

 a cover-glass, and let stand for partial evap- 

 oration; they are also used as the reagent of 

 a hanging drop, in volatility tests above an 

 alkaline solution on a cavity slide. In the 

 latter case the test-slide is in general rein- 

 verted after exposure to the vapor (of up to 

 two hours), and evaporation to a higher 

 content of the non- volatile acid then occurs. 



(6, 7) HsBile reagent in (1 -f 7)HC2S04; 

 6 direct application, (7), volatility test 



(8, 9) HAuCU in (1 + 2)H3P04 , (20) 



(10, 11) 1.3 HoPtBre in (1 + 3)H3P04 , 



(20) 

 The two following reagents are also used for 

 volatility tests (the first permitting rein- 

 version, but the second only as a hanging 

 drop) : 



(12) HaPtCle in (1 + 3)H3P04 , (20) 



65 



