Intelligence and Miscellaneous Articles. 235 



peculiar odour and elementary composition. The yellow substance, 

 soluble in water, crystallizes from a concentrated solution in trans- 

 parent needles ; the quantity formed is however so small, and it 

 deliquesces so readily in the air, that its chemical constitution has 

 not been hitherto sufficiently examined. 



The above -related experiments on the action of acids on curcu- 

 mine readily explain how turmeric paper becomes of a brown colour 

 by the action of concentrated acids, as well as by that of alkalies. 

 The concentrated acids dissolve the curcumine and form a brown 

 solution with it. — Ibid. 



[There is, however, this difference between the action of con- 

 centrated acids and that of alkaline solutions upon turmeric paper : 

 water immediately removes the colour occasioned by the former, but 

 not that produced by the latter. — Edit.] 



ACTION OF ALKALINE SUBSTANCES ON CURCUMINE. 



Curcumine forms compounds with the alkalies, which are very so- 

 luble in water. When powdered curcumine is treated with caustic 

 potash, a brown mass results which is very soluble in water. The 

 curcumine is completely precipitated from this alkaline solution by 

 diluted acids. Dilute sulphuric acid occasioned a precipitate in the 

 alkaline solution, which, when sufficiently washed, had the proper- 

 ties of pure curcumine. 



According to the observations of M. Kartner, it is not the alkalies 

 and alkaline earths only which change the yellow colour of cur- 

 cumine to brown, but the salts of lead, uranium, boracic acid and 

 borates occasion the same change in a greater or less degree. 



The shades of brown produced on turmeric paper by the alkalies 

 and alkaline earths do not materially differ from each othef ; they 

 depend on the concentration of the alkaline solutions employed. 

 All weak acids restore the original yellow colour of turmeric paper 

 browned by the alkalies : this happens simply because the acid com- 

 bines with the alkali, and thus decomposes the brown compound of 

 the alkali and curcumine. Turmeric paper, browned by a salt of 

 lead, has its colour very readily restored by dilute acids ; but when 

 altered by the salts of uranium the colour is almost black, and the 

 yellow colour is not restored until the paper has been immersed in 

 tolerably concentrated acid for nearly a quarter of an hour. 



A solution of boracic acid in alcohol alters turmeric paper to an 

 intense orange colour, which is not removed by the action of any 

 other acid ; but when touched with ammonia, it assumes for a short 

 time a fine blue colour, which soon disappears by the volatilization 

 of the ammonia. This blue tint is also more or less shown by im- 

 mersing paper browned by boracic acid in solutions of alkaline sub- 

 stances. 



A solution of borax renders turmeric paper blackish-gray ; the 

 neutral borates of potash or ammonia impart to it a less intense gray 

 colour. — Ibid. 



