1 64 THE SIMPLER NATURAL BASES 



Glycocyamidine, like creatinine, gives Weyl's and Jaffa's reactions ; 

 there is, however, this point of difference, that whereas the red or yellow 

 coloration produced by creatinine, sodium nitroprusside, and caustic 

 soda is discharged by acetic acid or changed to green on boiling 

 (formation of Prussian blue), glycocyamidine yields with acetic acid a 

 stable burgundy red coloration. 



Guanidine. 



Guanidine is a strong base, absorbing atmospheric carbon dioxide 

 to form the well crystallised carbonate, (CH 5 N 3 ) 2 . H 2 CO 3 , soluble in 

 water but not in alcohol. Of the salts with mineral acids the nitrate 

 CH 5 N 3 . HNO 3 is among the least soluble ; it forms large plates, melt- 

 ing at 214. 



The picrate, CH 5 N 3 . C 6 H 3 O 7 N 3 , when pure forms characteristic ir- 

 regular aggregations of leaflets ; m.p. 3 1 5, on rapid heating up to 320. 

 The solubility in cold water is I : 2630 at 9 and the salt may be used 

 for the estimation of guanidine (Emich [1891]). From complex mix- 

 tures, particularly when arginine is present, guanidine is not so readily 

 precipitated by picric acid ; the arginine should first be precipitated 

 by alcoholic picrolonic acid solution, and then, after removal of the 

 excess of picrolonic acid from the filtrate, the guanidine may be pre- 

 cipitated by aqueous picric acid (Kutscher and Otori [1904]). 



The picrolonate, CH 6 N 3 . C 10 H 7 O 5 N 4 , dissolves in excess of alcoholic 

 picrolonic acid solution (separation from arginine, above). With 

 aqueous picrolonic acid an amorphous precipitate is formed, which 

 crystallises from hot water in clusters of thin needles ; m.p. 272-274 

 (Schenck [1905, 2]). 



The aurichloride, CH 5 N 3 . HAuCl 4 , forms deep yellow needles, little 

 soluble in water. 



With alcoholic cadmium chloride a double salt CH 5 N 3 . HC1 . 2CdCl 2 

 results; m.p. 390-395 (Schenck [1904]). 



Guanidine is precipitated in the "arginine" fraction by silver 

 nitrate and baryta as a silver compound CH 6 N 3 . Ag 2 O which may be 

 crystallised (Kutscher and Otori [1904]). Guanidine salts in con- 

 centrations down to O'OI per cent, give a white or pale yellow precipi- 

 tate with Nessler's reagent ; arginine gives a similar precipitate. 



Methylguanidine. 



Methylguanidine may be synthesised by heating cyanamide and 

 methylamine hydrochloride in alcoholic solution to 60-70. It forms 

 deliquescent crystals. The nitrate, C 2 H 7 N a . HNO 3 , forms rhombic 



