G40 ZINGIBERACE^. 



so far disorganized that they no longer exhibit the usual appearance in 

 polarized light, but are nevertheless turned blue by iodine. The starch 

 has been reduced to this condition by scalding. 



Resin likewise occurs in separate cells, forming dark yellowish-red 

 particles. The entire tissue is penetrated with yellow colouring matter, 

 and shows numerous drops of essential oil, which in the fresh rhizome 

 is no doubt contained in peculiar cells. 



Chemical Composition — The drug yielded us (1876) one per 

 cent, of a yellow essential oil, which contains a portion boiling at 

 250° C, answering to the formula C"H"0 ; this liquid differs from 

 carvol (p. 306) by being unable to combine with SHI The other 

 constituents of curcuma oil boil at temperatures much above 250° ; we 

 found the crude oil and its different portions slightly dextrogyrate. 



The aqueous extract of the drug tastes bitter, and is precipitated by 

 tannic acid. 



The colouring matter, Gurcumin, C^"H^''0^ may be obtained to the 

 amount of ^ per cent, by depriving first the drug of fat and essential 

 oil. The powder, after that treatment with bisulphide of carbon, 

 is gradually exhausted, according to Daube (1871), with warm petro- 

 leum (boiling point 80° - 90° C). On cooling chiefly the last portions 

 of petroleum deposit the crystalline curcumin. Its alcoholic solution is 

 purified by mixing it cautiously with basic acetate of lead, not a.llowing 

 the liquid to assume a decidedly acid reaction. The red precipitate 

 thus formed is collected, washed with alcohol, immersed in water, and 

 decomposed with sulphuretted hydrogen. From the dried mixture of 

 sulphide of lead and curcumin the latter is lastly removed by boiling 

 alcohol. 



By Ivanow-Gajewsky (1873) the best produce of curcumin is stated 

 to be obtained by washing an ethereal extract of turmeric with weak 

 ammonia, dissolvinof the residue in boiling concentrated ammonia, and 

 passing into the solution carbonic acid, by which the curcumin is 

 precipitated in flakes. 



After due recrystallization from alcohol curcumin forms yellow 

 crystals, having an odour of vanilla, and exhibiting a fine blue in 

 reflected light. They melt at 165° C. Curcumin is scarcely soluble, 

 even in boiling water, but dissolves readily on addition of an 

 alkali either caustic or carbonate. On acidulating these solutions, a 

 yellow powder of curcumin is precipitated. Curcumin is not abinidantly 

 dissolved by ether, very sparingly by benzol or bisulphide of carbon. 

 It is not volatile; heated with zinc dust it yields an oil boiling at 

 290° ; fused with caustic potash, curcumin affords protocatechuic acid 

 (page 243). 



Paper tinged with an alcoholic solution of curcumin displays on 

 addition of an alkali a brownish-red coloration, becoming violet on 

 drying. Boracic acid produces an orange tint, turning blue by addition 

 of an alkaline solution.^ This behaviour of (impure) curcumin was 



^ The following is a striking experiment, on addition of a slightly acidulated solution 



showing some of these changes of colour : of borax and drying assumes a purple Ime. 



— Place a little crushed turmeric or the If the paper is now sprinkled with dilute 



powder on blotting paper, and moisten it ammonia it will acquire a transient blue, 



repeatedly with chloroform, allowing the This reaction enables one to recognize the 



latter to evaporate. There will thus be presence of turmeric in powdered rhuljarb 



formed on the paper a yellow stain, which or mustard. 



