Intelligence and Miscellaneous Articles. 233 



will be plane-polarized, according to the common law, but they will 

 each undergo a change of phase ; and the vis viva of the two rays 

 together will be equal to that of the incident ray, the vis viva being 

 measured by the square of the amplitude multiplied by the propor- 

 tional mass. 



In conclusion, the author states a mathematical hypothesis, by 

 which both the laws of dispersion, and those of the elliptic polariza- 

 tion of rock crystal, may be connected with the laws already deve- 

 loped. 



XLI. Intelligence and Miscellaneous Articles. 



ON CURCUMINE. BY M. VOGEL, JUN. 



TO obtain the colouring principle of turmeric root, the author 

 treated it, reduced to powder, repeatedly with boiling water, till it 

 nearly ceased to be coloured by it. The dried residue, thus deprived 

 by water of its mucilaginous, gummy, and a part of its extractive 

 matter, was repeatedly boiled in portions of alcohol of specific gra- 

 vity 0*8 ; this dissolved the greater part of the colouring matter, but 

 it is not possible to extract it totally, for the turmeric powder al- 

 ways remains coloured; the alcoholic solution is to be filtered when 

 cold, and is of a deep brownish-red colour. A portion of the alco- 

 hol is to be separated by distillation, and the residue is to be evapo- 

 rated to dryness in a porcelain capsule. A brown viscid mass re- 

 mains, which retains some brown extractive matter and traces of 

 chloride of calcium, which is one of the salts that the root contains. 

 To separate these two substances, M. Pelletier's plan was adopted ; 

 this consists in treating the residue with boiling aether, which be- 

 comes of a brownish-yellow colour. The extractive matter, which 

 resists the action of the aether, is of a black colour, and attracts 

 moisture from the air on account of the chloride of calcium which 

 it contains. The decanted aether ought to be slowly evaporated, 

 and after cooling, brownish-red fragments remain, which readily 

 fuse, and may be poured into stone moulds or on glass plates. In 

 this state the curcumine, when heated to redness on platina foil, 

 does not leave the smallest residue of inorganic substances. 



Attempts were made to volatilize the oil which the odour of the 

 curcumine evinced that it still retained, by repeatedly fusing it ; but 

 as this method did not succeed perfectly, another was tried, which 

 led to a more satisfactory result. 



The residue obtained by evaporating the aethereal solution was 

 dissolved in alcohol, and on the addition of an alcoholic solution of 

 acetate of lead, a red precipitate was immediately formed ; the salt 

 of lead was added as long as precipitation occurred. When this 

 precipitate is washed and dried, a reddish-yellow powder remains, 

 which consists of the yellow colouring matter and oxide of lead, the 

 proportion of the latter varying from 43 - 67 to 56 - 33 per cent. To 

 separate the lead, the powder is to be diffused in water and treated 

 with hydrosulphuric acid gas ; when the action of this is complete, 



