APPENDIX TO CHAPTER III BETAINES 145 



is much less soluble in water (in 25 parts at 100); it melts at 123; 

 when anhydrous the melting point is 213-214. 



The normal aurichloride, C 9 H 15 O 2 N 3 . 2HAuCl 4 , forms large orange 

 yellow crystals, m.p. 184, by crystallisation in the presence of dilute 

 hydrochloric acid and excess of gold chloride. Reuter mentions two 

 other gold salts of abnormal composition. 



Ergothioneine. 



For the preparation of the base according to Tanret [1909] 

 ergot is extracted with 90 per cent, alcohol ; after evaporation of the 

 alcohol, the aqueous residue is freed from fat and resin by filtration ; 

 20 per cent, sulphuric acid is then added to precipitate colouring 

 matters, and after removal of the acid by baryta, the filtrate is precipi- 

 tated with basic lead acetate. After filtering again, the excess of lead 

 is removed with sulphuric acid and the solution is made alkaline and 

 extracted with chloroform to remove the complex ergot alkaloids. It 

 is then acidified with acetic acid and precipitated completely with a 

 warm 8 per cent, solution of mercuric chloride. The mercury precipi- 

 tate is filtered off, washed, suspended in a large bulk of water and de- 

 composed by hydrogen sulphide. After removal of the mercuric 

 sulphide, the filtrate is evaporated under reduced pressure to a syrup 

 from which ergothioneine hydrochloride soon crystallises. After 

 washing with alcohol the substance is recrystallised from water. The 

 yield is O'l per cent, of the ergot employed. From the hydrochloride 

 the base can be obtained in various ways, for instance by boiling with 

 excess of calcium carbonate, filtering, concentrating and adding alcohol. 

 The free base is recrystallised from boiling 60 per cent, alcohol. 



Ergothioneine crystallises m leaflets and needles containing two 

 molecules of water of crystallisation. It is soluble in 8.6 parts of 

 water at 20, but requires more than a thousand parts of boiling 95 

 per cent, alcohol, and is insoluble in ether, chloroform and benzene. 

 The base is dextro-rotatory, [a] D = + 1 10. The melting point on the 

 Maquenne block is 290. 



Ergothioneine does not act on litmus ; the salts are precipitated 

 even in dilute solution by potassium mercuric iodide, by iodine in 

 potassium iodide and by mercuric chloride. With sodium p-diazo- 

 benzene sulphonate a cherry-red coloration is produced (Pauly's 

 histidine reaction). The most characteristic reaction is with excess 

 of alcoholic iodine solution which forms crystals of a less soluble iodide 

 (p. 46). On evaporation of the alcohol these crystals take up iodine 

 and become steel grey or blue. 



10 



