APPENDIX TO CHAPTER III BETAINES 143 



in pale orange-yellow prisms with varying water content. In con- 

 tact with the aqueous mother liquor, the anhydrous needles which 

 separate from a hot solution are transformed into the four-sided tables 

 with 4H 2 O. This constitutes a test for betaine [Trier, 1913,5]. It 

 is possibly dimorphous (Willstatter [1902, 2]). 



The aurichloricU, C 5 H U O 2 N . HAuCl 4 , is the most characteristic salt 

 and is dimorphous (Willstatter [1902, 2])- 



(a) Regular system ; from a 5 per cent, solution in hot water on slow 

 cooling, best in the presence of a slight excess of gold chloride ; it 

 generally separates in dull yellow, star-shaped aggregates ; m.p. 2OO- 

 209 (uncorr.) according to the rate of heating. 



(b) Rhombic system ; bright yellow leaflets, prisms and plates with 

 one truncated angle ; m.p. 248-250 (uncorr.). This form always 

 separates in the presence of hydrochloric acid. 



By recrystallisation from pure water a pale yellow salt of an inferior 

 gold content is obtained, possibly due to admixture with a hydrated 

 salt. For purposes of identification it is therefore best to recrystal- 

 lise from O'5-i per cent, hydrochloric acid, in order to obtain the 

 rhombic variety of high melting point (Willstatter [1902, 2], Fischer 

 [1902]). 



The mercurichloride, (C 5 H U ON . HC1) 2 . HgClj, is fairly readily 

 soluble in water, sparingly in alcohol. 



Stachydrine. 



The preparation of stachydrine from Stachys tubers and from 

 orange leaves was carried out bySchulzeand Trier [1909, l]by purify- 

 ing an aqueous extract with basic lead acetate, precipitating the bases in 

 the filtrate with phosphotungstic acid, removing the " histidine " and 

 " arginine " fractions of the recovered bases by means of silver, again 

 precipitating the bases from the filtrate of these fractions as phospho- 

 tungstates, extracting the recovered hydrochlorides with absolute 

 alcohol and then precipitating with mercuric chloride ; the stachy- 

 drine is separated from choline by Stanek's method (see p. 151). 



The yield from fresh tubers of Stachys was 0^036 per cent, of 

 stachydrine; from dried orange leaves 0-19 per cent. The tubers 

 also contain a minute quantity of trigonelline. Jahns [1896] isolated 

 stachydrine by means of potassium bismuth iodide (Kraut's reagent). 



For the properties of the base and its salts consult Schulze and 

 Trier's paper [1910, 2]. Like other betaines, the base loses a mole- 

 cule of water of crystallisation at 100 ; the anhydrous base has the 

 composition C 7 H 18 O 2 N and melts at 235. Stachydrine is readily 



